Neptunus Rex ...... I think we can safely say that was a bite
However, it does go to highlight what a minefield these occasions can be, and which can as a result really detract from both the host and guests' enjoyment. I would never consider 'necking' an ale during an At Home evening - a BBQ possibly, but not an At Home. Rather than worrying about drinking from a bottle, I would be more concerned with spoiling a good beer. As PN suggests, a decent beer tastes far better when served in a glass, especially the continental beers which I prefer over the typical British gnat's piss that is Carling or John Smiths etc. that is unfortunately so prevalent this side of the Channel.
And whilst a guest should ensure their behaviour isn't such that it prevents a repeat invitation - unless it really is that painful - a good host will always ensure their guests are fully at ease, and will recognise that not everybody 'appreciates' a single malt or a glass of wine, and might prefer something else. Outside of a formal function, I see nothing wrong with quaffing a decent beer from a glass if one so desires, especially if it is offered.
I am reminded of an occasion where I was having dinner with my then girlfriend (a wannabe oenophile) and her parents; I don't know whether she was more mortified by her father (a 1*) offering me a beer with dinner or me for accepting. Her father was firmly of the view that dinner should be enjoyed and not endured and that to insist on white wine with fish, red wine with meat and a glass of peat passing as a dram after dinner was little more than snobbery. Secretly I think he was quite pleased to have an excuse to break out the beers over a rather indifferent bottle of wine!