The problem isn't lolnexus, you're doing the same thing Riot does: focus on the symptom and not the cause. The simple question you need to ask yourself is - why do people lolnexus their teammates in champion select?
The answer is simple but has two possible sides - first, they could be looking for trolls or horrible feeders to decide whether to dodge. In that case they probably aren't going to even say anything, they are just going to dodge. Second, they are looking at lolnexus to see if you're good at a role, probably to convince you to let them play <insert role> instead because "you're a trash <insert role> let me carry".
So the problem is that Riot matches people at random based on a generic matchmaking rating without any consideration for what position they play or their skill per position. So when multiple people on a team "main" the same role it creates tension, arguments, frustration and also puts you at a disadvantage if the other team isn't in the same situation. That's toxic and players here in NA are pretty immature so they don't handle mistakes or poor play very well.
Riot desperately needs a role queue, voice communication, to fix the division/tier system and to make at least your personal MMR for each queue visible.
