Two reasons. First, people and organizations that are wrongly criticized deserve to be defended, even if on balance these are people and organizations with whom one disagrees on many matters. That's especially so if the wrongful criticisms come from people who are at some broad level of generality in one's own political camp. If liberals are wrongly faulted by conservatives, we conservatives should correct those errors. (Don't argue please that liberals don't do the same when the shoe is on the other foot; some do and some don't, and in any case their failings wouldn't excuse our failings.)

Second, as I've said before, I often disagree with the ACLU, and I sometimes even condemn it with some force for its actions. I want to have company in such expression, and many readers of this blog are natural sources of well-founded condemnation of the ACLU.

But we'd both open ourselves up to making false allegations (which is bad itself) and look foolish (which is bad instrumentally) if we fall into a visceral hostility to the ACLU that clouds our judgment, and leads us both to ignore the correct positions that the ACLU takes and to misstate the ACLU's supposed errors.