Yes, unfortunately it is true, pubs seem to be bastions of sexism. I visit pubs on a regular basis, sometimes alone and I've lost count of the number of occasions that I've experienced Henrietta's experience. There is no doubt that it can be slightly humiliating and that you are left with either accepting the humiliation or creating a scene and none of these should be acceptable. You learn not to care about it but that's wrong as well.
The other thing that I've observed is that some men speak/behave in such a sexist way, when they are within the confines of a pub. It is conduct that I do not experience anywhere else.