There is a difference, though. Wegener had an alternative theory. As far as I can tell, those "skeptics" don't have any good alternative explanation (or data),

There is a difference, though. Wegener had an alternative theory. As far as I can tell, those "skeptics" don't have any good alternative explanation (or data), just a gut feeling. So they are not at all in the same position as Wegener. Catastrophic claims do no good, that's true. But frivolous skepticism (without a good counter-theory) has policy implications (continuing business as usual, which is unsustainable). The scientists opposing AGW are not being mass criticized for their scientific opinion (because they don't have any), but for the policies they give support to. I also disagree with your interpretation of climate gate, but let's leave that.