Why does a person that's already made up their mind start insulting you if you want to think on it for a while?

They fear that you taking the time to think first, will give you time to find the answer that will get them to change their mind, which will make them look like an ass, which they obviously are, or they wouldn't need to resort to abuse, instead of acceptance.

yeh because i could pop some catfish into the lunchroom's microwave and let it explode.

WUAHAHAHAHAHAAAAAAAAAAA!


then leave the mess.

Trolling.
It shows an attempt to at least think critically by taking time to digest an argument(and few people here do it).

Because they lack the ability to formulate reasoned and reasonable thought?

A coarse upbringing, I should imagine!

Cuz they are an asshole