If someone asks a dumb question do you try to make them look a bit intelligent by giving an even dumber answer?

Nope.  I just skip them over.

No.  I tell them they are a dumbass and not to waste my time.     I don't suffer fools. 

I work in computer support; it's impossible to give a dumber answer to some of the questions I get. I usually give them the right answer since it's my job.