Hello! I agree with with Jennifer. To say that something is legit (which is almost like a slang shortened version of legitimate) in this context means that it is "able to be defended with logic or justification; it is proven to be valid". So the speaker is saying that the person should not have been "down-voted" because the question was a valid one. I hope that helps!

"legit enough" here means a "good enough" reason or a "valid" reason.