I may have got completely the wrong end of the stick here but, here goes.....
I suspect that the issue that some* people have with first class travellers is that they've not paid much of a premium for some of the promotional/off peak/advance tickets and seats. This opens up 1st class to higher loading which is probably not as quiet as some might hope. It also eats away at the differential between 1st and standard, thereby making 1st less "special", thereby opening it up to people who - how should I say this - may not appreciate the perceived ambience and behave according to how others may wish them to in the rarefied atmosphere.
It's not the travellers' fault at all. They're merely availing themselves of what's for sale. Good for them.
For a long journey not involving London I, however, go by car. 1st or standard - I hate sharing my space with so many others.
*Does not include me or, probably, most on the forum.