Atheism is a form of religion...

[One Above All]

Is religion bad on the basis that it's a religion?

Yes

Because, if so, christianity and every other religion - past, present, and future - are bad.

Yes, and the three Abrahamic religions especially.

Is it somehow less valid as a PoV because it's a religion?

It's invalid in method and that all but guarantees the inevitable accumulation of additional errors as that PoV progresses (or fails to).

I agree with everything you said, but here's the kicker: theists don't. When they regurgitate "arguments" like this, they don't realize that either they're saying all religion is invalid/evil/wrong, or they've said nothing of value (akin to telling someone right next to you that there's a slight breeze - a fact they've undoubtedly noticed and knew about before you finished your sentence).