We had this topic some months before, or at least a part of it. Turns out some people are offended when the enemy just leaves and doesn´t say "gg". If you consider that a rude attitude, I can´t help you. If I didn´t enjoy the game, I won´t write "gg". Why should I lie?
Insults on the other hand are very rare - for me at least. It´s best to ignore that, because most of those players are usually <20 years old and there´s no sense discussing with that.
What´s more common is people complaining about the game and how it´s not balanced. I don´t consider that rude either.
I am <20 years old, i assume there is no point in discussing with me?