People like the author of the OP are incapable of seeing patterns. Why were “tankies” worried about US backed regime change? Even when the regime being overthrown has committed warcrimes?

Maybe because US and it’s proxies like Pissrael always use the ensuing chaos to promote their interests at the expense of innocent people. And the most convenient proxies are not principled organizations, but instead people who will commit violence on innocence without hesitation. And the US always prefers those regimes because they weaken the region and facilitate western hegemony.