Partly, the world has indeed changed to accept straight guys to wear nail polish and other feminine things. Some guys who do this they do it because they need more attention from women or simply they just want to be neater. On the other hand, such things can only be seen in places where people have forgotten their traditions.
Look at most screamo bands. They come with tight pants, guy liner, eye shadow, nail polish and sometimes lip gloss. OR you can look at the hair metal bands of the past (poison, montley crew, kiss, ect.) and it was excepted back then too. Its all about what is considered "fashion" that week
I believe that as long as you're happy with the way you look then so am I. It's not up to us to judge others and the world would be a better place if we all just didn't look at people on the outside and judge them for how they look. I hope this helps
Personally I think men and women should dress however makes them most comfortable (would potentially include nudity in that, but there are actual health/safety concerns that make that not such a good idea for most people). The key I think, for doing any of that though, is to do it with confidence. If you act unsure, or worse take offense if someone calls you on it, then people will continually look at you like it's weird. But if you own it, and act like it's the most perfectly normal thing in the world, then people generally don't cause as much of a fuss about it.