I have not noticed anyone "telling people what to read", in the sense of saying "You should read X. you should not read Y". Nor do I see anyone telling people what to write – what would be the point; are they at all likely to listen? I see people saying things like "I think X is a better writer than Y", or "in my opinion Z is overrated", or "such and such a genre does nothing for me". But that really isn't the same thing as telling anyone what to write and read, is it?
From personal experience, which we'll come to presently, I would say the real trouble is that people take poetry criticism absurdly personally, and I don't mean criticism of their own poetry. For many people, if you admit to disliking a favourite writer or poem of theirs, it is as if you had peered into their firstborn's pram and exclaimed "God, that baby's ugly!" Passionate as I am about my own favourites, I do not get this. If someone told me he thought the poems of Paul Henry, or the novels of Barbara Kingsolver, were no good, I should think the less of his judgement, but I wouldn't be personally offended – I should probably just conclude that I had the better taste, though I would try not to say so.
But I know all too well that this isn't the normal reaction. It is why I try, these days, not to comment on poems quoted in posts unless I like them (I don't always succeed, if it's a writer I viscerally dislike, but who's perfect?) There's an American writer whose Wise Words are often quoted on my newsfeed. I find her a bit trite and sentimental; she isn't greetings-card verse by any means, but as serious poets go, I would describe her as entry-level. I don't, because not only would there be no point, I'm aware that some of her fans would immediately take it as a personal attack on their own taste and judgement, rather than simply a refusal to share said taste and judgement.
I know this because the only approach to hate mail I have ever had results from my having disowned a poem that, though it became unusually popular for one of mine, displeases me by not being, in my view, subtle enough. I haven't tried to withdraw it from circulation at all; I just don't give permission for it to be reprinted in books, except very rarely for charities and not always then. But it's out there all over the web; I'm not depriving anyone of anything or stopping them reading it if they want to.
All I have done is voice, on my own website and blog, my own view on the thing. Now I have read a lot of fan fiction, some of which was not only better written than anything the original writers could manage but truer to the characters and spirit of the source. So I don't subscribe to the primacy of the author. (Dumas thinks, and often says, that Aramis is worldly, selfish and amoral. He's wrong.) But you would think the author had as much right to an opinion on his/her own work as anyone else. Not, however, according to some of the email I've had. "I get very cross whenever I read what you say on your website about this poem". (Yes, the quick solution to that problem is staring me in the face, too…) "You must try to like it" – aye, there's the "must" word at last.
I think what they are really saying is "you must validate my judgement, or at least not publicly dissent from it". Why they would need such validation I don't know. But I don't think this attitude does poetry criticism much good. I'll be honest and say I don't go along with the view that "it's all subjective". I do think there are valid ways of assessing how effective someone's use of language is. But even if you did not accept this, it would surely be valid to voice an opinion and by doing so, you would not be telling anyone what to read or write, merely what you like to read and write yourself.
I used to have to persuade first-year students that it was OK to voice reasoned criticism of someone else's poems – it was not "rude" or "insensitive", nor was it true, as one once said, that "you can't criticise something when it's sincere and heartfelt" (oh yes you can, it if happens also to be inept, or at least less ept than it might be). It was an attitude most of them grew out of. And yes, criticism can become uncivil and sometimes unfair; replying to such criticism is what correspondence columns are for. But in itself it is not some sort of personal insult to the fans of what is being criticised, much less a prohibition on what they choose to read. It is a disagreement with their taste, certainly, but since when was that illegal?