We are all different. Since I would not accept this, I dont know how or others do...Whatever floats their boats

You need to know who you are, what you want and your values and importance in life. You need to be consciously aware/mindful where you put your foot in, type of environment you are getting yourself into. The environment where you put yourself in will become your world, it will influence you as it will change your perspective, attitude towards things.

Just know that there are pros/cons whenever one choose certain path. There are benefit and cost in each choice you make and you need to know them to make rational choice.

There are things one can take it lightly and they are things that needs to be taken seriously and you need to be able to make that judgement for yourself.

Also dont underestimate the power of habit. People who say/do things often get into habit and they are very hard to break. Like alcohol/drugs, sex can be addictive and can take hold of ones life.
I hardly doubt that those who stay in open relationship (sleeping around) for long period of time can actually adapt well into closed relationship or marriage later.

Some ppl start using alcohol/drugs with attitude of experimentation (to try something new that brings pleasure) for short term. But in most cases, they all become long term users because of addictiveness in the substances. Sometime, attitude of take is easy can be the very thing that burns someones life down.

People surely have free will, meaning they can do whatever they want with their lives. But if one knows and understand that when there is action, there is reaction, there are cost and benefits, possible consequences for ones words/actions, and on top of that there is the complexity of interconnections with others around us (unless one cut ties with family, friends, rest of the world and isolate oneself), considering all that factors, although we are free, we are not really free.
We are not an animal; we need to be able to control/discipline ourselves, knowing the possible consequences/cost for our action (before taking such action) and see if it is in-line with what we want and value (be prepared to face the possible consequences) and if not, than we should be able pull the break ourselves, overriding short term benefit for long term. (or decision that has higher cost than benefit).

Only2bestrong - is there a reason youre remaining in this situation with this man if you obviously disagree with a lifestyle that clearly affects you and your relationship with him?
Should you continue, please get checked for STDs regularly and use as much protection as possible. You can never be too careful, even if you are accepting of that sort of lifestyle.

I haven't even been with this man and never will. I just found out that he is in to open relationships when I posted.

Some people accept it because they don't think they have a choice, think they can't do better. Sharing a guy is better than not having one at all. For some women like a single mom who's busy with her kids and life maybe it works for her for a while, she has some adult time but no commitment if she's already got a lot on her plate and doesn't have time to invest in a relationship. I'd say it rarely works for long. In your case I'd stop contact with this guy because all he wants is to have sex with a lot of different women. The moment anyone of them wants more he'll drop them like a not potato. Not to mention disease or the chance of someone ending up pregnant unless he's been neutered! Lol

I am not a big fan of open relationship because to me the majority of the time one or both people are truly not fully aboard this relationship status and it causes lots of major problems. But I do not see a big difference between being with someone who dated many women or men and open relationships because you have to be open to the idea that men and women have had partners before you came into their life.

Yuck,
To the defenders such open relationships please read the initial post ,
The scumbag started dating only2best without telling her right upfront ( honest and open with the truth ) that he was an open relationship kind of guy

So he is a scumbag manipulative dirt ball

So typical to hide the truth until --- it comes out, or serves a self centered purpose .

I judge people that are manipulative self centered underhanded sneaky pieces of shit.

Beware of wolves in sheeps company ....

And for modern times no god crowd...

You are what you eat
So in sex
You are who you eat

Garbage in garbage out

I saw a group of ppl similar to what you have described in your post before. the feeling i got from them was that... they were like a zombie. something felt disconnected, not me with them per se but within themselves.
They were out of touch with their innerself... they had lot of emotions but didn't have/know their feelings.
I do believe this is one of the cost/consequences for their action. the "numbness of feelings" in long run.
Regardless of who in the open relationship (the player who sleep with many other within same period of time or the other person who sleep with player), in the long run, i think there will be some mental/psychological consequnces for their choice/path/lifestyle. Changes such as how they view themselves, how they view such activities, their personal intake on any future experiences/event that may come their way and i think it will also change their perspective/attitude/beliefs on any future relationship they will have onwards..hence pretty much effecting one's whole life. And i doubt that these "changes" are good/positive ones.
numbing one's own feelings is like getting rid of any opportunities to feel any genuine happiness in one's life.

The original question was how someone accepted this...

It depends on who you are, and sometimes the people involved.

I think there's a difference between polygamy and open relationships.

Most, not all, but most open relationships don't work.
Many, again not all, polygamy relationships can work.

If you're a hippy- like, love everyone, kind of person a relationship with multiple lovers for both partners/spouses can and does work for some.

If you're not comfortable with it though it's not for you, and you wouldn't accept the situation.

Simple as that.

I am not cut for open relationships if I have feelings for the person. If the person is only my lover and feelings aren't part of the agreement, I do not care who else he sees besides me. Also, I find that people freak out over the concept of open relationships yet a huge number are in one and they just don't know it. But if it's not for you, get out. You only know what you can or can't handle.

In my professional experience "open relationship" means or leads to NO commitment.
Sex is is not safe these days Besides the emotional abandonment when your partner loves another. Self respect is way more important than being linked
..

I am not sure what happened. I guess maybe he got the point I wasnt in to open relationships. Last night he sent me a message telling me maybe it just was our time. He does want to hang out with me soon told me to hang tight next thing I know he blocked me from facebook and blocked all my phones and text messages. No explanation of anything