I played a game last night where someone was completely convinced that LRMs now are trash and that even disciples can easily beat them. When I tried to tell him otherwise, that LRMs are still very very good, he proceeded to make wild claims about various things he'd read on the forums.

The fact is, the forums have a heck of a lot of posts that are completely untrue. A lot of people are claiming various things to be completely unbalanced/unbalanced when in reality, it's closer to the opposite. The reason for this is multiple.
1 - Newcomers. There are those who are still learning how to play and don't quite know the various strategies and counters yet and when they encounter something seemingly insurmountable, they immidately think it's imbalanced.
2 - Spreadsheet theorycrafters. These people will look at just the numbers and imagine their effects in game. The problem with this is that there's many other factors that they often fail to take into account such as ships turning, accel, max speed; range; unit combinations; player skill; etc.
3 - Bandwagon jumpers. These people usually view themselves as one part of a community that they often believe is "polarized". Once attached, they'll relentlessly agree and argue for their position even if they're completely wrong. Often, I've found, these people use ad hominem attacks in leiu of an actual argument that they don't have.
4 - "Elite" normal players. These people have gotten a false sense of their ability. They've been mainly playing against people who are new and completely crushing them. They then draw conclusions that would otherwise be untrue had the played against tougher opponents or people who really knew what they were doing.

I'm not providing a solution for any of this but I want people to be more aware and actually TEST the stuff they read. If someone says light frigs can now beat LRMs 1v1, don't take their word for it - try it out first. This actually goes for everything you read and learn. Critical thinking is the key.  The proliferation of this misinformation REALLY needs to stop.