Before I can talk about the flag, I have to talk about a couple of other things. The first is elitism. It's a term we all hear often enough, but what does it actually mean? Of the various dictionary definitions, "persons of the highest class" is the most relevant here. Emphasis on class. To be in a class means to be separate from - almost always above - others not of that class. Elitism is the idea that there is a class of people, usually defined by possession of some quality, that should expect deference from everyone else. The most commonly mentioned kind of elitism is intellectual elitism, but there are certainly other kinds and in fact those accusing people of intellectual elitism are just as elitist themselves according to some other standard. For example, many Christians consider themselves to be part of a moral elite. They don't use the term, but the belief is quite explicit in many denominations all across the theological spectrum. By contrast, the military does explicitly use the term in reference to a physical elite. Police officers often partake of both moral and physical elitism, which is part of why they're both so honored by some and reviled by others. Basically, everyone is an elitist of some sort, because everyone believes that whatever traits they personally value most (often by the most amazing coincidence those they believe they possess themselves) should be valued most by everyone.
That brings us to the second thing: virtue signaling. What does it mean to put an emblem or slogan on one's shirt, or car, or anywhere else? At first it might seem to be no more than an expression of belief, appreciation, or enthusiasm. So far, so good. However, none of us flaunt symbols of every virtue. We prioritize. For example, I'm pretty well known for wearing shirts with some sort of message. Usually the message is primarily humorous, but it's a very particular kind of humor that shows my appreciation or enthusiasm for intellectual virtues having to do with things like science or literature. I don't wear shirts praising bravery or honesty, even though I consider those good things. Thus, part of the message is that I value these particular virtues more than others. Another part is that it identifies me with a "tribe" of people who might share similar priorities. Somebody who wears a flag or a cross is pretty clearly signaling a different set of priorities, and membership in a different tribe. That's all OK, we all do it, except...
Here's where I actually start talking about the flag. What's wrong with people displaying the flag on their clothes or their cars? Well, for one thing, it's almost certain to be a violation of the flag code as defined in 4 U.S.C. § 1 and following. If you're going to honor something, you have to do so on its own terms, and I dislike hypocrisy even more than I appreciate patriotism or just about any other virtue. Second, there's the issue of priority. When you choose one virtue to treat as primary, and potentially as the basis for defining an elite, you necessarily de-prioritize others. I happen to think patriotism is a particularly weak virtue. That's not to say I consider it a negative virtue, but would I put it above other virtues like rationality, justice, honesty, or empathy? No, no, no, no. Hell no, times four or however many it takes to make the point. I believe those who put patriotism first are misguided, and those who flaunt its symbolism are signaling membership in a whole tribe of misguided people. By the way, the founders of this country would probably agree. Patriotism is another word for nationalism, and they shed blood in opposition to the British nationalism of their time. They certainly held other values, such as rationality and freedom and justice, above pure naked nationalism. Excessive nationalist symbolism dishonors what those symbols stand for.
I don't really hate the flag. When it's used in its original and appropriate fashion, such as at military or sporting events, I totally respect it. What I hate is flag fetishism. When somebody uses the flag in a way directly contrary to what it stands for, in particular to identify with (and therefore exclude others from) an elite defined only by the display itself, that just makes me ill. If you want to honor the flag, show me that you also honor "all men are created equal" and "e pluribus unum" and all the rest. Otherwise, what you're wearing might look like a flag but it's functionally a swastika.
P.S. What I just said about flags goes double for MAGA hats - the true dunce caps of the modern world.