I concur.
Yeah, social media and even speaking itself are for sharing opinions, but there's a way to do that with politeness, tact, and compassion. Do they not have the empathy or the imagination to understand what it's like to be excited for something, just to have people who hate it, barge in with nothing to offer but their hate for the thing?
Haven't you ever gone to an anime convention, all excited for your hobby, especially during the years when we still had to hide our affinity for anime or else be mocked, only to overhear randos---who actually paid to also attend the anime convention---loudly badmouthing anime? Just unabashedly saying aloud, in the middle of an anime convention, that they don't like anime? This isn't hypothetical! I've heard it many times! It is such rain on a parade, only outdone by how little sense it makes. Please imagine liking ANYTHING, being in the middle of enjoying it, just for weirdos to interrupt with their rants about how stupid and gross they think it is.
But at the same time, these people advocating for "social media to be for expressing opinions" probably wouldn't walk into a sports stadium, telling everyone there how they hate sports. You don't go to the tomato soup club to shit on tomato soup. You go to the tomato soup club to enjoy tomato soup with others who enjoy tomato soup. In reality, I don't even like tomato soup, but I have the imagination to imagine what tomato soup fans might feel if haters of their specific favorite thing, just killed their buzz with their unsolicited hate comments. It would be one thing if they could give their opinions with consideration and empathy, but some people who decry "So I'm not allowed to share my opinions?!" often aren't interested in using empathy when they interact with others. ...Maybe trampling on others' feelings is more important to them than their actual "opinions". Otherwise, they'd learn tact, persuasion, and at the very least, how to express themselves with consideration for others.
In case it wasn't clear:
Don't tag your hate posts with the name of the character/series/thing you hate. It's more natural to assume that everyone who uses that tag, loves that thing. You don't want to be the asshole who barges into the cake store for cake lovers, just to blather about how you hate cake. Please make up your own "#anti[thing]" tag.
But also, in the specific case of the original post. I don't think that saying they dislike tomato soup, into the general void of the internet, is the same thing as breaking into the tomato soup club, just to rant about how "tomato soup sucks". Now, posting with #tomatosoup, just to say "tomato soup sucks"...THAT would be barging into the tomato soup club, just to rant and ignore empathy and consideration.
But also, I get how the comic artist in the quote retweet might be part of the population that sees the dislike of tomato soup (or other subjectively dismissible thing), as such an inconsequential thing, that going through the effort/trouble of mentioning it, when it seems not worthwhile to even mention, can feel like impoliteness.