Because once that door swings open a little bit... who knows what might bear some scrutiny?
Who made the clothes you're wearing? Or your phone? Were they a slave? A child? Are they even still alive, or do they have cancer because of the factory where they worked? Do their parents miss them, if they're gone?
What happened to make the chicken sandwich you had at lunch? Are you complicit in slow torture unto death, just by existing in the modern world?
Better to keep the door shut tight, and attack the messenger if anyone has anything to say about it. We're just making music here. No torture, no killing, no profit from the destruction of lives. Just music! Trust me. Enjoy.
(I don't think most people are like this. I actually think most people in the West at this point are against the "war" in Gaza, to at least some tepidly inactive degree. But certainly, also, a lot of people aren't against it, q.v. this article.)