Erm, IMO it depends on the age of the child.
I used to have milky tea in a sippy cup when I was a little child and it was lovely and comforting.
I am neither a "northener" "chav" or any such. .
My DD has had tea in a sippy cup, very weak, organic decaf, with either milk/goats milk/rice milk. Don't see the problem.
IMO it's not the same as giving coca cola, squash or similar in a bottle.
And yes, my DD does still use her bottle. Some children like dummies, or a blanket as a comforter - hers is her bottle. However, she now just drinks water in it. I don't see the problem really.
My philosophy is they won't be doing it when they are 25! I also, unless it is shoved in my face, couldn't really care less what other people do with their children. Live and let live. It's not like they are beating their children with a stick, is it?