Well, it depends I guess... If the tutorial is more like a show and tell of someone's technique/workmethod, there's not much to critique is there? And usually artists will say something like; "this is just how I do this, it's by no means perfect".
But in the case of an actual step-by-step tutorial, teaching people to use a certain tool or program, I think tutorial writers should be open to critique. People should be able to point out mistakes for instance or show them a different way of explaining or writing for example
As long as the person giving the critique knows the difference between critique and criticism, it's should be fine.
I think people should be open to critique, but others should also not be so critical. A tutorial has to be taken at face value from an artist as the method in which THAT artist achieves the specified goal, and not necessarily the best way to achieve that said goal. I also think that the idea of "Realism must trump style" is getting out of have and making things boring and bland. Art is all about an artist showing off something they see or think to the world through a different view. While it's very admirable for an artist to be able to create beautiful photo-realism, look at how some of the most revered artists in history did anything but. It was their creativity that people admired. If you want realism you can look out the window, but you can never achieve what some artists will show you simply by viewing the world as-is. Art, in the end, is all about what it conveys and how it makes you feel.
I strive to be a "better" artist (though maybe not as grind-stone as I should), but I have to stop and ask myself if just because the art is cleaner, or more realistic... does that make it "better"? I believe the creativity behind it is where the substance comes from. If I run across a pony picture (for example) that throws anatomy or proportions out the window, but makes me stop to look at it and think "That's interesting" or "different", then hasn't it achieved its goal of art more than something that looks pulled out of the show?
I'm certainly not advocating that artists don't learn things like anatomy, because understanding how anything works can help with creativity. But sometimes not knowing how something works can keep you from being stuck in the mindset of normalcy, too; you don't know where the edges of the box actually are, after all.
Yes and no. If you are wired on a certain 'style' and see something not complying to it then chill out. Also noting the writers style makes a difference, some people just have their own way of doing things and THAT'S OK. Taking into consideration the many possible variations should also be done. But no matter what or why you critique it the way you come off (even if you don't mean too be however) means a lot. Offensive usually equals defensive, and the tut. maker may feel like their's is oh-so-good and they are doing everyone a favor. I'm not saying ALL are like this, but many people are upset when you challenge them on their high horse. So taking things into consideration and wording your crit carefully has a LOT to do with it, but yes I do believe tutorials and their writers should be open to constructive criticism.