Obviously you can downvote whatever you wish.
I don't agree with downvoting @quackwatch simply because of their OPINION.
I mean, really, @quackwatch thinks we're idiots and we think @quackwatch is an idiot.
I really don't see the difference.
Just believing someone is an idiot is NOT a good reason to downvote.
Are all christians idiots?
Are all muslims idiots?
Why would we expect to NOT be downvoted by (high-powered) accounts that disagree with us and yet still downvote accounts we disagree with?
It just doesn't seem very "principled".