I think indulging in healthy rivalry over inherently trivial matters is fine, and good even. (It's basically the core philosophy behind organized sports.) Just so long as things are kept civil and the importance of which isn't blown out of proportion. I do find it generally uncouth that to talk something up, people feel the need to make a negative comparison to something else, so I see your frustrations and apologize for inflicting that. But that's also something that is just human nature and something everyone does and is hard to regulate and/or untrain yourself to do all the time. I also think it's not something that's inherently bad, it is a natural part of the human decision making process. It's just the way that you do it that makes it bad/toxic. And I think that you can definitely go too far in policing tone to the point where dissent and negative emotions are never given a home/venue for expression which is a different kind of toxic and unhealthy, but I digress.
For what it's worth, I'm not from NY, I'm from CA - I'm used to everyone and their mom saying our pizza out here is dogshit, so I figure it's all fair game/in good fun.
I really don't understand why people feel the need to attack it like it'll make their regional pizza style better somehow. Just let it coexist and talk about what's good about your favorite pizza instead.
This is a philosophical matter that I've actually thought a lot about. Like all things, I'm sure the reason is complicated and varies from person to person, but pizza is in a unique position in American culture that naturally brings this kind of competitiveness out in people. For me, the two biggest reasons are:
1) Basic sports-brain: Yes, people ought to value and respect each other's food/cultural/regional preferences, but competitive drive and tribal affiliation is part of human nature and something that can be enriching and rewarding if harnessed responsibly. Competitive sports is an obvious realm of this, where people can get heated up about something ultimately trivial, and then when it's all over go back to being friends/coworkers/etc under a mutual understanding that it's all just a game with no real impact or stakes in everyone's everyday lives. Competitive multiplayer video games is another realm of this and works to varying degrees depending on if the people involved can regulate themselves enough to stop saying gamer-words at each other. But this kind of regional competition extends to pizza in an almost unique way in the food world. Most "regional" food is truly limited to a specific region due to long traditions (North-East seafood; Southern BBQ; Tex-mex; etc) and/or is pretty standardized across the country due to modern distribution and the power of the Information Age. Pizza is a food that has unique regional traditions all over the entire country, and those traditions have spread and mixed thanks to the steady/rapid flow of people and information throughout the country.
2) Pizza is a uniquely shared food: Most of our culinary experiences that have been crafted in this country have been touched by how they're consumed. Most people when going to a restaurant wouldn't share a bowl of soup among each other because the nature of the food itself doesn't lend itself to sharing easily with our cultural moores. Yes, you can divy up soup into smaller proportions, but if everyone is just getting their own bowl, everyone can also just order their own bowl and cater it to their own tastes. Most meals are like this when you go out to eat. There are also of course, individual-sized pizzas. But most people going out (or taking out) specifically to eat pizza in a social setting, will get one to share. And we do this in a way we don't do this with the vast majority of other foods. And our culture is not particularly adept at sharing/handling compromise when everyone is otherwise ordering their own food to eat for themselves at all other times. With a pizza, you have to pick a style/toppings that everyone can agree to. And that's going to inevitably lead to rankled feathers on occasion, when some people feel they're compromising too much, or being asked to pitch in for something they don't even like. Ordering a pizza as "half and half" helps some of the time, but you can't get a half-deep dish, half-thin crust pizza. So that low level of resentment from the failures of compromise can build up and help inform people's opinions. I know it's affected mine. I wish I could get back just some of the money my friends forced me to spend on pizza I didn't like, and all those unpleasant experiences have definitely affected my willingness to eat those other types of pizza over the years.
Deep dish is a great sometimes food. it's heavy as hell and I don't order it very often, but it's nice to have available for when I want it.
I have often made the joke about deep dish being a casserole, not a pizza. I only half mean it. I do think that for myself, a lot of the appeal of eating a pizza is in the experience of eating it as hand-food. Especially when coming from a cultural background where hand food is generally looked down upon: it was always fun to get a legitimate excuse to eat food with my hands as a kid. So it always felt wrong or dissatisfying to eat a pizza with a fork and knife. But deep dish pizza is to me, a lot like having a burrito over a taco - they're still going to taste good, and they're still mostly the exact same ingredients that taste pretty similar once it's all being smashed up inside your mouth. It's just the different delivery system and which one you prefer on any given day that makes the difference. I actually like deep dish just fine, but it's never my default and rarely would I choose to pick that way to organize the ingredients over another.
Another reason for why my appreciation for deep dish is lacking these days is because I've relatively recently developed GERDs, and anything with tomatoes sets it off hard. Pizza in general has become tough to swallow (literally) but deep dish is like an extra level of stomach abuse when the amount of tomatoes and sauce in a deep dish is generally way higher in proportion to other styles of pizza.