I went through exactly what you're describing and had no choice but to cut certain folks out of my life to preserve my own serenity and peace of mind.
Here's one real sign that your "friend" is not really your friend.
If they only complain and talk about them self and never ask you about your own feelings they are NOT a friend.
Cut that person out of your life!

Good for you for realizing this at a young age, it took me longer to wake up.

until they tried to pick one with me

I understand what you’re saying, but I have to wonder what you bring to the conversation? Do you just stay mute while they continue to talk? Do you ever volunteer anything about your own life? I know a couple of people who are those types who don’t talk very much. In fact, they often seem incapable of carrying on a normal back-and-forth conversation. It’s tedious trying to have one with them, because I feel as though I have to keep it going or it would just not exist. As a result, I’ve ended relationships with both of them because they just simply didn’t do their share. So you see, there are always two sides to every story.

When you really love someone so much you can't always help but put them on a pedestal, and look past every wrong and red flag in them. Parents especially do this a lot with their kids. You don't always get the wake up call of who they really are until they purposely do something to hurt you. You get a slap in the face by their dark side. You still love them, but you can never really trust them again. It can take a very lot of time to get over these things and move on depending how deeply you felt for them. Don't go breaking hearts just because you know you can.

Nothing wrong with disagreement... but should you ever put someone on a pedestal like that? Even if you were a parent, would it be good for your own child? I've done the same and felt the slap, darkness, and greys with someone I had unmatched passion for. I know the fall was because of the radical/euphoric love I indulged in at first. Still think they're great.
And curious, at the OP and other complainers, what is it you do with your prized peace of mind? As someone who spends a slothful amount of time thinking, what's this peace of mine of yours and what do you do with it? When one of my friends pisses me off, I usually talk to them and then ignore them if they aren't receptive and (secretely) content with their own problems.

Some people will play for the attention, and blame the other person for being naive, not caring that it was wrong for them to play another in the first place. Some people don't consider another person's feelings. They're only concerned about what feels good to themselves.