Ownership isn't a free pass to do whatever you want, and the neighbors can suck it.
The problem is that in many areas the land use restrictions are very similar to regulated businesses, there to protect those who came first and don't want competition or others near them. While I think a shipping container is absurd I want to know, what is the restriction on building a house there?
If you can properly secure it, demonstrate its structural integrity, fire safety etc then it's usually fine.
Though, even under those circumstance, how would you feel if you were a beekeeper who had carefully curated and bred your hives for years, you moved, and all of a sudden your bees, whom you see as lovely helpful animals going out and literally making flowers bloom every day, are ordered destroyed because your neighbor has an allergy? Ownership isn't a free pass to do whatever you want, but it's equally false to imply that nobody has any ability to assert their own interests, or as is the case here, novel ideas over the status quo.
I think ownership really does make a big difference here because if he were just dumping a container into a park because he can afford a shipping container and moving it to a park, that'd be very clearly dickish. If he built a wooden gazebo after buying the lot with lots of hostile armrests so that the homeless couldn't shelter there, nobody would care at all and the neighbors would probably love it. It seems like he's done a slightly more flamboyant and slightly more humane version of the gazebo. Putting glass in the windows was a bad move from the start, but they're probably better as shutters or open-air anyway. In a year, it probably wouldn't be bright red at all, because local graffiti artists would have covered it larger pieces and it would look exactly as the community of humans using the parkspace dictated. (Assuming he doesn't just paint over the graffiti, which would truly be a dick move.)
The same, no. But on the same spectrum — namely, a property owner acting unilaterally, his neighbors' concerns be damned — absolutely.
Do you legitimately think that's not thumbing their noses at their new neighbors? Do you actually believe that the neighbors – you know, the folks who were there first — have no choice but to suck it up? "Welp, they bought the house and moved in. Nothing to be done about it now."
If, on the other hand, you mean suddenly dropping over for tea and scones of a weekend morning, or fruity pink drinks after work, then no, I don't think they're obligated to "suck it up". Their neighborhood, from their perspective, has just been "invaded", and they have a legitimate right to feel aggrieved by that, right or wrong, bigotry or not, assholery or otherwise.
Just like the folks in Lincoln Heights have a right to feel aggrieved by Rhinehart's ugly, unmaintained container — except, of course, that the gay couple didn't break any laws. (Just a few years ago, they might have, depending on jurisdiction, but since Lawrence v. Texas, there isn't even that; it's just confrontational, and possibly even rude.)
I'm also doubtful that the gay couple truly hasn't broken any laws. I'm sure that with enough digging, the homophobic neighbors can find a fence on the wrong side of the property line, a deck that isn't zoned properly, or something similar; the neighbors could even pass a HOA regulation prohibiting pride flags. Does that make it morally justified, because it's "their" homophobic town? It seems like you think so.
Would you call it confrontational for a KKK member to move into a black neighborhood and fly Ol' Dixie? Because that's perfectly parallel to your proposed scenario, and that's what you're arguing for.
Just because the people we're talking about are members of a protected class doesn't change the logic of the situation.
People need to calm down. You're more likely to die of lightning strike than bee sting in the US.