Just a short examination of something I tend to think about - why people seem to take an insult against something they enjoy personally.
I think the root of the problem is the perspective of "it's good because I like it" - which isn't true at all. Just because you like something doesn't make it inherently good. There's nothing wrong with liking it anyways - if it's something that makes you happy, you should like it. Anyone that tries to tell you otherwise is either an asshole or jealous of your happiness (possibly both). I personally like a lot of stupid things - I know they aren't good, but I like them anyways. Why? Because they make me happy, and that's all the reason I really need.
Now, that isn't to say we shouldn't be critical of the things we like - quite the opposite. By acknowledging that something you like isn't necessarily good, you're already looking at it objectively. We should always be critical of the things we like - it's how we improve them. That's why the "it's good because I like it" mindset is actually harmful - it buries flaws in works and causes people to perpetuate those same flaws in new works, since they're touted as things that are "good".
Consider cliches - there's nothing wrong with liking cliches, but you still need to acknowledge that they aren't necessarily good. Otherwise, you end up with books, shows, and movies that are nothing but cliches, because cliches are perceived as being inherently good because people like them. When utilized sparingly, and in the right context, cliches are fine and work well - so they can be good, but not always, since they can often show a lack of originality. Creative ideas include turning cliches on their head, or subverting tropes - but just because someone doesn't use cliches also doesn't make their work good.
This is why it's important to be critical of the things we like - there are no clear, one way answers to what is and isn't good. As I've heard many a time in writing, everything is a rule until it isn't. But I'm getting a little off track.
The other problem with the "it's good because I like it" mindset is that many people with this mindset think their mindset is "I like it because it's good", which is why they become so reluctant to accept that something they enjoy isn't, in fact, good. To have a true mindset of "I like it because it's good", you have to be critical - which means accepting flaws and weaknesses in a work along with its strengths. Just because a work isn't perfect, doesn't mean it isn't good. But refusing to accept that there are any flaws in a work is a good indicator that you aren't being critical, and therefore think something is good because you like it, rather than you like it because it's good.
Rather than worrying about how "good" a work is, I prefer the mindset of "I like it because it's enjoyable". After all, the most important thing about a work isn't really how good it is, but how much you enjoyed it.
To come back to the opening statement - the reason, I think, that people feel personally insulted when someone insults something they like is because they feel their judgement - and therefore intelligence - are being called into question. Since we often judge people based off their intelligence - and by intelligence I more mean academia, since it's not critical thinking but sheer body of knowledge that's judged - people feel a need to justify why they like things. Because if you like something stupid, you must be stupid, so the things we like can't be stupid.
Which is a weird argument, and a stranger way to think, but certainly something people get ridiculed for.
"You like pumpkin spice lattes? What a basic white girl... I bet you're completely unoriginal and post inspirational quotes on Instagram thinking you're changing the world."
"You like anime? What are you, like, five? Stop watching cartoons."
These are only two examples I can think of off the top of my head, but ones that highlight my point. There's nothing inherently good or bad about pumpkin spice lattes or anime in their own right, but people get ridiculed just for liking them. And it makes sense to want to defend the things you like, but when you try to say something is good when it isn't, it just makes you look worse.
This is another reason it's important to be critical of the things we like - but more importantly, a reason to be kind.
There's no need to insult someone personally because they like something you don't - and, in a funny turn of events, just because you don't like it, doesn't mean it isn't good. It just means you don't like it. I don't need to tell anyone to be critical of the things they don't like - but I feel it is important to remind people to be objective of the things they don't like. Just as the mindset of "it's good because I like it" is harmful, so is the mindset of "it's bad because I don't like it".
Going back to cliches - cliches can be bad, such as when the plot of the story revolves around them or they're used in place of actual storytelling. (Unless it's satire, in which case, it could be very entertaining.) But just because a work involves or contains a cliche doesn't make it inherently bad. You don't have to like it, but be objective of whether or not that makes it a "bad" work or not. And never call or imply someone is stupid for liking something you don't like - you wouldn't want it to happen to you, after all.
As a closing point, here's a review I wrote about the movie The Fountain, because implying that the reason someone doesn't like a work is just because they don't understand it (and therefore are implicitly or explicitly stated to be stupid) also doesn't make a work good. Especially when the people making this argument can't seem to explain what makes the movie good past their "understanding", which implies they don't understand, but want you to think they do so that they look smart.