It applies to LoL as well, just not as constantly. If you act like that, people just won't want to play with or against you.
Even if you're Challenger, or Diamond like this guy, if you're attitude is trash like this, then no one will respect you, nor will you be allowed in the LCS. So it's as if you have achieved nothing. That's why you're unsuccessful.
Bad behavior is always very limited and dull since if you act like that constantly to everyone, then no one will like you and people will hate you leading to self demise. Good attitude is always right, because it's limitless and people will respect you and help you, leading to real improvement and just gives you the advantage. It's even shown on animals. The only thing bad attitude and sadism gives you is trouble. So it's just dull thinking that this will make you satisfied. You will soon suffer and no one will care that you've achieved anything. You can also check this video on YouTube: "Nice Guys Finish First".
It even works like math and the laws of physics and the universe:
Good to Good: + & + = + (positive)
Evil to Evil: - & - = + (positive)
Evil to Good: - & + = - (negative) (this is also known as sadism)
Good to Evil: + & - = - (negative) (and this is also known as masochism)
I will one day be Diamond like this bronze-attitude douche and will feel accomplished because people will respect me and I'll inspire them to climb the ladder. Not make them feel like this game is filled with assholes with no life.