Well people can criticize your writing style/subject as well. Like if someone wrote a lame cliche song about puppies in bubble gum... wait that'd be kind of funny... but like a Backstreet Boy song I'd feel free to criticize them about the choice of their topic and writing style. And if you don't like his criticism you are free to disregard it, but you can't really say constructive criticism is wrong in any circumstance as long as the person is offering your opinions.
And the fact is some people just think the content of pretty much any death metal (or whatever) is over done and cliche. As are a lot of subject and styles of lyrics I suppose.
But as I've said already don't post lyrics if you don't want people to criticize the style of them. Writing is not only about the order of the words its also about the content of the words.