
People are obsessed with social rules. The second you tell someone they either can't or must do something they want to know the exact reason why behaviour X is acceptable and behaviour Y is not. You'll be instantly hit with a barrage of how social rule X conflicts with social rule Y, or benefits social group A over social group B. This would be easy to pin on geekish behaviour, were it not for the huge wodges of ettiquette guides published over the centuries.
The objections mostly boil down to "I wouldn't mind people doing that to me.", "They don't mind doing it to themselves." or "I don't see why anyone would be upset by that." all of which miss a fundamental point. The reason for social rules is to avoid offending people. If you do not mind offending other people then feel free to refer to people of African origin as Niggers, wolf whistle at women in the street, tease people for their red hair, refer to people unfortunate enough to have learning difficulties as retards, be aghast that people who arrived in the country last year don't speak English without an accent yet, demand that families who live in slum tenaments pay for medical treatment rather than having furniture, complain that gay people insist on flaunting their sexuality in public and generally act like it's the 18th century and the damn peasants are making a mess of your lawn.
Which isn't to say that being offended trumps everything - you will find people who will be offended at _everything_. And at some point you will almost certainly find yourself saying "I do not mind offending this group of people at all, and frankly, I rather enjoy offending you, because you're scum." But bear in mind that emotions are rarely rational. Telling someone they shouldn't be offended, because their friends of the same call them "My Nigga." so logically it must be ok for you to do it, is not a good approach. They are offended, they have their reasons, and your choice is simply to decide whether this person is someone you wanted to offend, or not.
Reducing the great mass of social rules down to one simple one has benefits - it can be applied in all situations, for instance. But it also removes clear answers from situations, because it depends on moment-to-moment interpretation rather than the simplicity of "X is always right, Y is always wrong.". Offense is personal - one person might be fine with being ogled, another might not be. You can't be sure from a distance, and while one person might be advertising their sexuality by wearing low-cut tops because they want the attention, the next might simply be too hot to wear a burqua that day. Personally, when out in public I try to err on the side of caution, in order to avoid making people I don't know feel bad. When I'm with people I know, and who know what my sense of humour is like, (and I know that they're ok with what I'm saying), I'm much happier to relax and say things that would get me lynched in other circumstances. You may find other tactics work better for you - but you'll have to experiment to find out.
The one thing I do know is that attempting to apply any rule to groups of people is doomed to failure, and protesting it won't make you any friends.