“Sealioning” is a bad-faith “debate”1 technique, popularized by Gamergate, in which a person asks irritating questions under color of innocent inquiry. These questions often take the form of leading questions in the vein of “When did you stop beating your wife?” (Or, as one of the comments to the above-linked article observes, when you’re in Tea Party country, the question is, “Why are you opposed to a balanced budget?”
The term originated from this comic. A person who doesn’t respond to questions asked in this bad-faith, passive-aggressive way are presumed to be unable to support their position.
1. I put sarcastic quotation marks around “debate” because Gamergate types aren’t interested in debate; they’re really interested in arguing. As this person notes, Gamergate types—and those from other Chan-style bulletin boards—assume that all normative statements are invitations to argue.