"You do you, and I'll do me." This is a phrase that has become increasingly popular in today's increasingly "tolerant" culture. This is called moral relativism: The moral worth of an action can only be found in the eyes of the actor. It is intolerant and disrespectful to claim that someone else's actions, or positions, are wrong. However, the immediate problems with relativism are self-evident.
Suppose that I tell a thief that I think stealing is wrong. The thief tells me not to impose my opinions on him. Someone should immediately see the problem with this. The thief thinks that it is wrong for me to tell him that his actions (stealing) are wrong, so he tells me that my actions (the confrontation) are wrong. This is self-defeating. He wants me to stop telling him that his actions are wrong, so he tells me that my action is wrong. The error is obvious, but the thinking permeates everything surrounding college life. It is amazing how often someone tells me that I cannot respectfully share my opinion with them because what they do should not concern me. (Note: I am obviously not advocating for any disrespectful or inappropriate confrontation.) They tell me that thinking that someone else's actions are wrong is disrespectful. One more time: They think that I should not be thinking something because it is wrong to think that someone else should not think something. I am suggesting that you should not suggest things.
"You can think that what someone else is doing is wrong, but you shouldn't say anything about it because that is disrespectful." I would surely hope that, if I were doing something wrong or something that might be morally compromising, someone would tell me! If I cannot tell someone (with all respect) that what they are doing is wrong, then there would be no such thing as a criminal. He is not a thief, he is just "him doing him"? Obviously, if you are a moral nihilist or do not believe in objective morality, this argument does not apply to you. However, please be ready to accept the consequences of moral nihilism.
"But criminals hurt people in one way or another. What I mean is that you shouldn't tell someone what they do or think is wrong when it doesn't affect anybody." There are a host of things that we consider wrong that do not effect anybody. If you wanted to harm yourself, it wouldn't affect anybody else. However, I would hope that someone would try to convince you otherwise. Furthermore, I would hope that you thought that morality amounted to more than "it doesn't affect anybody."
Moral relativism is not tolerance, and it is not open-mindedness. It is not even extra respectful. It is simply a self-defeating position. Agreeing to disagree is different: It is the acknowledgment that two contradictory propositions cannot both be true, and the opposing opinion is unconvincing. It is not inclusive to think that two contradictory opinions are "equally valid." It is logically incoherent. When the law of non-contradiction is no longer assumed to be true, the consequences are boundless.
I will not think that you are right for thinking P simply because you think P, because to do so would be unreasonable. I can agree that we both disagree and will respect each other anyway. Being disrespectful is one thing. Being logically consistent is another.