Unfortunately, this is what happens when you get 'townies' taking up any activity or sport that involves the countryside. I'm not saying all city or town dwellers are ignorant litterbugs, but if you've been brought up in a vaguely rural setting, you tend to have a bit more respect.
When my Grandma and I use to walk around where she lived when I was about 3 or 4, we didn't stick to rights of way by any means, but we knew which farmers were tolerant and which weren't (there was one who shot any dog if it was off the leads in his fields, sheep or no sheep).
Close gates, don't litter, be considerate (don't tear-arse straight through herds of animals) and as a rule you should be fine.
I was at Cannock a few months ago and some dickhead rode by at the top of one of the climbs with his 'tunes' pumping out from mini-speakers mounted on his bars. Listen to music, fine - but to assume everyone else won't mind is just inconsiderate - unless you're an attention-seeker anyway (in which case I hate him even more)! And yes, his tunes were rubbish.