I've been here long enough to see this argument before, yes.
I feel the same as I do now: that if it looks like people are using the downvote as an "I disagree" or "I don't like you" button, people are entitled to call this out and ask for an explanation. If no good explanation is forthcoming, this suggests the downvoters might be in error.
I don't think he was telling you personally to STFU, but rather making the argument that if you really want immigrants you should argue for green cards, not H1Bs which give the employer too much control. I think you mis-read what he wrote. BTW, I've upvoted you even though we "disagree."
You didn't ask for an explanation. You complained. This is wrong.
"I find it incredible that, judging by the downovtes, people seriously think I am obligated to respond to someone who has shown so little respect to me."
This is not seeking clarification. You didn't even assume people were mistaken. You made a judgement call. You were complaining about down votes. Don't do it.
I feel the same as I do now: that if it looks like people are using the downvote as an "I disagree" or "I don't like you" button, people are entitled to call this out and ask for an explanation. If no good explanation is forthcoming, this suggests the downvoters might be in error.