The importance of good grammar

I try to use correct grammar in my stories -- I'm self taught so I don't pretend to get everything right every time but the caption to this video made me realise some people have a looser grasp of grammar than I do:

So you deepthroated your step mom? That means your step mom has a dick and you swallowed it.

I'm not judging -- I like a dick girl in my stories every now and then -- but I think, judging by the picture, you meant to say "My stepmom deepthroated me"

Grammar's important in these instances.