I'm not a fan of Russell T Davies either, so you're not alone!
My biggest issue is his overall portrayal of female characters. First you've got Rose Tyler, who I think he's written to be his ideal woman: white, blonde, pink loving, and girly - the ultimate feminine stereotype. The only way she gets any joy out of life is by getting a man.
There's a similar parallel to The Doctor and Rose's "relationship" in
Torchwood with Jack and Gwen's relationship. It's not quite as obvious, since Gwen doesn't visually adhere to the Barbie stereotype, but she becomes a pass around sex toy. Rhys is her Mickey and the only difference is that she made him forget that he learned about her betrayal and then went onto have a baby with him. (I won't be surprised if Rhys is the next to get killed on in TW though, just so Gwen and Jack and
finally 
be together.)
I feel that there are also extremely disturbing racial undertones, particularly with the way he contrasts his OTP of The Doctor and Rose with Mickey and Martha. The latter two both got treated worse than dirt, but at least he allowed Martha to get away and become engaged to Tom Milligan, a man that actually respected her. But for what? Just so she could break the engagement within a few months (within the
Who timeline) and turn around and marry Mickey? Now, personally, I think Mickey and Martha did deserve each other because they were both highly underrated characters who constantly got the short end of the stick. I was glad they ended up with people who would treat them right, the way they deserved to be treated. But I don't think that's why RTD put them together. I do think he thought they deserved each other, but for very different reasons then mine: I believe he viewed them as Rose and The Doctor's "leftovers," which is why I think he had no problem putting them together. This would have infuriated me no matter what color their skin was, but the fact that both Mickey and Martha were the first male and female black companions in DW takes the issue to a new level, because there was a concious choice to make those characters - who were always intended to be "leftovers" whether or not he always envisioned them ending up together as well - black, and yet his portrayal has always said to me: "This - Rose and The Doctor - is what you should strive for, while
this - Martha and Mickey - is not good enough."
Then there's also "Love & Monsters" in which RTD writes that the hero of the show advocates bringing a woman back to a partial life as a stone block, so she can "live" out the rest of eternity giving blow jobs. I couldn't even believe my ears when I heard that at the end of the episode. I was revolted.
Obviously I don't know the man personally and I can't say I don't like him as a person, but the recurring gender and racial messages in his writing really stand out to me and that's why, on the whole, I do not have a favorable opinion of him.
