I'm going to put a housemate's plate in front of his door after only a few hours
Why would you put his plate outside his door?
he can eat his own damn food since he does it to me, too.
You shouldn't be passive-aggressive about this. You should talk to them. You shouldn't put their food on the floor since that's gross.
That's true, I was hoping to see if he will be mad.
I'm glad you see that the behavior is wrong. I know you want to make him mad, but I'm sure you can find another approach in getting your point across to him.