If someone is insulting you...
just mute and ignore them!
If you decide to defend yourself, you have a lot of chances to become agressive too. Then, the report they do on you will be justified, because you insulted them. There is no reason to defend yourself against complete strangers. Don't try to find excuses (unless they specificaly target yourself, like "sry, I'm doing poorly"), especially if it's something like "I lost lane because you never ganked".
Being an asshole against another asshole doesn't make you the good guy : You're still an asshole.
