It is a double standard. The thing is, as you know, double standards often contain multitudes; double standards within double standards within double standards. I'm pulling this number mostly from my ass, but though the NRA spends something like 5x what AIPAC does, 1) like I said earlier, people somehow manage to be more nuanced in their gun commentary and 2) there is no obvious risk that the NRA will be situated into a racist/anti-Semitic/whatever conspiracy.
"Be weary of dynamics that exist in AIPAC discourse that don't exist in, say, NRA discourse" strikes me as a positive double standard.
Also, I think we're losing sight of the fact that Rep. Omar's mistake was kind of specific. It was to reflexively center, in a manner that was both incredibly reductionist and highly generalizing, an expression of support for Israel around money/AIPAC.
I said this earlier: when it comes to this topic, you're going to run into bad faith all day long. In my mind, though, there's not really any need for groundwork setting before saying "fuck AIPAC."
(Oh, and our explanations for AIPAC's influence pretty much align, I think. I just worded it differently.)