*sigh* If you want my honest opinion on stuff such as this, I don't give a flying f*ck if your character is going with canon and vice versa or what the hell kind of writing it is.
My main concern is if it's written WELL enough to be readable. Writing is all about being able to READ what you've written, not care about who's paired up with who.
Besides, I tend to screw around with slash pairings from time to time. And I have yet to hear someone b***h to me about it. You have to welcome things with open arms in order to understand and THEN you can set your own opinions.
I think the main reason why some people get mad about Mary-Sues or Mary-Gary is because when it's a Mary-Sue or a Mary-Gary...they tend to be written rather poorly. I'm not saying that you write poorly, but that's normally the prejudiced assumption which is why people are quick to frown at such things.
Also to some it's an annoyance to learn about a character. But people fail to realize that the writer is showing how they SEE a certain character. So they're basically re-learning a character anyway.
Most of the time, some people think that Mary Sues are too 'perfect' or too 'mopey'.
*shrug* I used to write Mary-sues before once upon a time when I was....ten...twelve...and they were actually really bad. sweatdrop So...I can understand why some people would