Hey there Helen,
This is probably one of the hardest issues to deal with. Personally I haven't encountered directly anyone directly making comments to me, I guess I'm lucky. I think the vast majority of people who would think of saying anything to your face are too cowardly to actually do it.
I'll be honest and say that it was one of my biggest anxieties, but now if it were to happen I would just ignore it. Realistically I don't have the time or inclination to address people who would make such comments, I have more important things to be doing as I am not going to be able to change this persons point of view or opinion during the brief moment of the encounter, so don't bother. I've started telling myself... "I don't mind and they don't matter.
Steph