You’re entitled to your opinion (and thanks for not coming at me all crazy with it, haha), so with that being said, I have to disagree with you on some points.
I don’t think RIB has ruined Sam and Mercedes as characters. They’re actually two of the better characters on the show, in my opinion. Two of the more mature characters, in fact.
Mercedes isn’t egocentric, which is a word that I think people abuse way too much. Does she think highly of herself? Yes, and she should. She has insecurities, but she’s not written as an insecure character. The only reason people go so far as to make her out to be egotistical is because she voices her desire to want a solo and believes she’s good enough to get one. And you know what? She is. And she has to voice it/fight for it because it’s been proven in the past that she’ll be looked over otherwise. She gets looked over because there are characters (like Rachel) who also speak up when they want to be featured and fight for it just as hard, if not harder…and sometimes with more drastic measures.
Mercedes hasn’t stopped being there for her friends, hasn’t stopped encouraging them to be better than they think they can be, and hasn’t stopped believing in them. Case in point, her recent leadership skills displayed with the Troubletones. She didn’t act like a tyrant, she gave credit where credit was due, found a place for everyone (including Sugar—who’s in a show choir and can’t sing) and everyone was happy. A lot of people say she “stole” Santana and Brittany away from New Directions, but they weren’t being utilized to the best of their ability either, so it made sense for them to go where they could shine.
What I find is that people tend to confuse going after what you want, no matter what other people think, with being egocentric, and that is so far off the mark. Yes, taking other people’s opinions into account before taking action is good. No, you don’t have to let other people’s opinions dictate your wishes/goals/hopes/dreams. That’s how people end up in old age, regretting the things they should have done when they were younger. No one is going to like every choice you make, and it’s not easy to go after what you want, knowing that you might hurt someone (especially when it’s your friends/family), but that’s just a risk you have to take. People won’t hold that against you forever. Mercedes is making choices based on what’s right for her and what’s going to make her happy, and people do that every single day. That’s the way life is. You can not let other people dictate your happiness. And you know what? People STILL like her. Love her, even. As far as I can tell, she has no enemies on the show.
When it comes to Sam, it looks like your main concern with him is that he’s leading Mercedes to cheat on Shane and that he’s not as honorable as he used to be. Sam is very much still a good guy, and it’s evident by the way he took Rory under his wing, befriended Blaine (even after that really crappy comment Blaine made to him), and he’s even friends with Quinn, who DID cheat on him (and helped him out later). Sam is so past high school drama and it’s so obvious in the way he carries himself, the way he interacts with characters (notice how he didn’t get mad at Santana when she insulted him after his return—season 2 Sam would have been taking a hard, long look at himself, trying to figure out what was wrong and tried to change), and the way he’s trying to get Mercedes back. “Back” is the keyword there.
The thing is, Sam and Mercedes never actually ended. They were torn apart by the circumstances and just because people are separated by distance, doesn’t mean that the feelings are just going to go away. He’s not trying to get Mercedes to cheat on Shane. A lot of people seem to be confused about that, too. He’s trying to get her to own up to the feelings that she keeps denying and is poorly hiding. Shane is obviously a rebound and a safe option for Mercedes, and the fact that she didn’t break up with him the second Sam returned really shows that she is not one to break loyalties (another PLUS for her character). Also, Sam has never said anything about Mercedes cheating on Shane, and he’s not going to. In the past, when characters have cheated, there has been no confusion about whether or not it’s going to happen and it happens quickly. If Mercedes was going to cheat on Shane, it would have taken place already. All Sam has said is that he’s going to fight to get her back (woo her, impress her) and in his mind, Shane doesn’t even come into the equation. The final decision is all up to Mercedes, and Sam has put himself in a position to possibly get his heart broken because she can still say no. He didn’t take that option away from her.
I guess I found all of your assessment wrong, really… Sam and Mercedes are at their best right now and their development is only making them better. I’m excited to see how everything plays out. They aren’t horrible people, like the way you kind of make them sound. If there’s something wrong with speaking your mind and going after what you want (without compromising other people), then let me know right now, because apparently, I’m living life all kinds of wrong.