Basically, for objectivists (with respect to morals), having some other morality is wrong. For relativists it's merely different. The former is a much stronger cause for intervention than the latter.
Also, willingness to insist on your morality is generally a sign of taking it seriously.
The correlation between moral objectivism and interventionism is probably true, but I think it's historically contingent, and not a logical consequence of objectivism. Whether or not I think of my morality as objective (universal) or subjective (a property of myself), that's orthogonal to what I actually think is moral.
I'm a moral relativist. My morality is that torture and murder are wrong and I am justified and, indeed, sometimes enjoined to use force to stop them. I don't think this is an uncommon stand.
Other people are moral objectivists, but their actual morals may tell them to leave others alone except in self-defense.
Recently, James_Miller posted a conversation between Sam Harris and Scott Adams about Donald Trump. James_Miller titled it "a model rationalist disagreement". While I agree that the tone in which the conversation was conducted was helpful, I think Scott Adams is a top practitioner of the Dark Arts. Indeed, he often prides himself on his persuasion ability. To me, he is very far from a model for a rationalist, and he is the kind of figure we rationalists should know how to fight against.
Here are some techniques that Adams uses:
Overall, I think what Adams is doing is wrong. He is an ethical and epistemological relativist: he does not seem to believe in truth or in morality. At the very least, he does not care about what is true and false and what is right and wrong. He exploits his relativism to push his agenda, which is blindingly clear: support Trump.
(Note: I wanted to work on this essay more carefully, and find out all the different ways in which Adams subverts the truth and sound reasoning. I also wanted to cite more clearly the problematic passages from the conversations. But I don't have the time. So I relied on memory and highlighted the Dark Arts moves that struck me immediately. So please, contribute in the comments with your own observations about the Dark Arts involved here.)