This site is meant to provide a venue for rational arguments - test the ideas of others and submit our ideas to be tested. This is a source of joy and, much more importantly, the only viable way to achieve better ideas. Ideas, more than any other single thing, enable humans to make our way in the world.
Although fallacies, falsehoods and foolish ideas should be attacked without mercy, individual guests should never be. Ad hominem - trying to undermine an argument by belittling an individual - even thinly veiled i.e. "you don't know what you are talking about", "you're too political", ... will not be tolerated. Uncivil or non-constructive behavior may be grounds for permanent removal from this site.
Here is a competing view of Ad hominem which is far too lenient for my taste. The author is close to saying that any amount of off topic cruelty can be redeemed by an argument which tangentially addresses the issue. I am closer to saying that any amount of brilliant on topic elucidating argument can be undone by a casual insult.