I prefer "liberals have supported every war when the news told them to".

They don't see atrocities as the result of a system, just outliers, mistakes, bad individuals, and other things they can overlook.

Whereas showing them every single military conflict the US has engaged in since WWII, it's much harder for them to say "Oh, yes we were wrong all those other times, but Ukraine or China or Iran or is different"

I think the full quote is:

Liberals are against every war except the current one and they support every civil rights action except the present one.

Something very close to that effect anyway.