I disagree that leaving things unsaid is the best approach to online discussion, especially when it comes to soundbite level social media like Lemmy and Reddit. Doing this puts forth the position that only one thing needs to be said, which is underhanded and intellectually dishonest.
You're absolutely right that both mainstream parties in the US are closely related in policy, so it is a failure of those arguing against the Israeli genocide to not call this what it is: a governmental policy problem, not a single party problem. Saying "democrat bad, support Israeli genocide" while ignoring the opposite party just because it is not in power is a failure to point out the root cause of the issue. If we don't want to support any genocide, we need to make sure that no matter what party is in power, it doesn't happen.
I'll ignore the fact that you disagree with their economic policies for now and continue to focus on the fact that this is a systematic issue, not one that is beholden to one party or the other.
As a native Seattleite, I try my best to at least acknowledge people with a head bob. Sometimes I'm not feeling a conversation and just try to shut it down quickly.
"Your dog is beautiful!" "Oh yeah, haha, she's a good girl." - and keep walking