Both of these type of posts aren't really comments on the design style, the reckoning, the derbies, or what have you. If some one says, "I don't like the "Nevermore" shirt because it's an abridged version of the poem and the black letters against the gray shirt really don't work that well. It was a nice concept, but the execution wasn't all the way there," shouldn't that be considered a more worthwhile, and insighful, way of commenting on the shirt?
Nope. Because it's not true that things must have a respectful tone implying that believing the opposite is OK. If you go to make a sandwich, and the bread is moldy, and you make the sandwich anyway on green bread, expecting people to accept this as a matter of taste is naive.
Given the comments you have made on Nevermore in this example, give a logical argument why someone would still like it: They're a huge fan of poorly abridged poetry? They're a Poe fan who actually doesn't care about the content of his work and wants to show the world how little they care? They wanted an asphalt shirt, but couldn't justify buying a blank tee, and Nevermore's impossibility to see after a wash or two fit the bill for them?
If you cannot make a strong argument for your opinions, you have no right to expect respect for them. The Apple Jacks defense of "I just like it" is not a strong argument. Unless one is willing to have zero identity, they need to know why they like the things they like, and they need to accept that sometimes their reasons will be Sirius GPP, and grow thick enough skin to handle it.
You want rudeness eliminated so badly? No one is truly rude when they respect someone. Most of the people I am most interested in discussing things with are those who I don't fully agree with, but who have earned my respect by making intelligent arguments for their side of things. That makes conversation interesting and stimulating. You say "well, maybe someone wants Nevermore because they love the Raven". I say "why would anyone who loved the poem want a keepsake which so thoroughly adulterates it? It would make the wearer seem ignorant of the topic they love so much." You say "well, maybe they just like birds." I say "the number of people who like birds enough to have one made out of words which are truly meaningless to them slapped on their shirt, while possibly extant, is not enough to perpetuate the tee for over two years." And so on and so on. You have three choices: the first is to continue until you make a point strong enough for me to accept your rationalization, regardless of my agreement. The second is to continue until you realize that I can counter any point you make with a better one, and you accept that my reasoning is sound enough for respect. And the third is to whine about how I'm mean and can't I just let people like what they want? Most people choose the third, and the respect they get is paid in kind.
Why does it matter to me why someone likes something? Because it should matter to them why they like something. If it doesn't matter, why bother having the opinion at all? If it does matter, shouldn't it matter enough to know why it does? The "play nice" mentality stems from the insecurity inherent in being questioned. If you have no satisfactory reason to like Nevermore (and such a reason needs to include similar reasons as to why its undeniable shortcomings don't matter... it's not opinion that it fades super quick or that it's sloppily abridged), why should anyone accept your view as valid?
I believe there are magical tiger-elves, as yet unseen by man, which lay invisible eggs in meadows. When you step on an egg, you have good luck. Why do I believe this? I just do. Your basic ideology states that I have a right not only to believe this, but to not have the belief called into question as flat out wrong and ignorant against the facts (which I also refuse to address in relation to the belief). Sound extreme? The facts weigh heavily against Nevermore being a worthwhile tee (and certainly numerous tees could be in its place), and the opinions against it are all evidence and observation based. Just like a tiger-elf, there needs to be incredibly compelling reasoning on the other side before anyone of note is really going to believe it. If there isn't, you bring the mockery and insult upon yourself.