The ACLU defended the right of the Klan to march.

This is different than a Klansman being on trial for his car crashing into a bus stop full of black kids, and then publicly announcing before sentencing that "I'm only sorry I didn't kill any of darkies."

The Klansman's own words are used to show intent. Without them, he might legitimately argue that it was a honest accident. Maybe believably, depending on other evidence.

Using someone's own words against them in court is not a violation of freedom of speech. Intent matters, and that doesn't mean we have thought-crime.

Show me the case where somebody is prosecuted solely because "they think you're a dick" - as opposed to actually doing something criminal while being a dick - and you'd have much stronger case. I'm not aware of ACLU defending any criminal actions of the Klan. If we talked about Auernheimer's freedom to express his views, however vile may they be, it'd be completely different case.