Cyclists wear what they wear for the same reasons people wear whatever gear they use on a moto.
It's more comfortable and more functional than the alternatives.
It really isn't to piss people on motos and cars off.
There are plenty of jerks riding bicycles, but if you did an objective survey, there are probably more piloting motos, cars and trucks. After all, there are lots more of those on the road than bicycles. I know I see them every day.
As for the tax thing, I pay with my car taxes, the moto taxes and the taxes on the fuel they burn, and when I ride my bike I'm not putting anywhere close to the damage on the road that the car does. And whether I use my car or not, the tax is paid.
If it would end the lame argument about paying for the use of the road, I'd gladly pay a registration fee for my bicycle. But no one has made the decision to require that. If you want that, tell your gov. officials.
Let's put registration stickers on every pedestrian's butt too while we're at it. There are no sidewalks within 5 miles of my house, so all the people walking are using the road for free too. So is my neighbor's horse, leaving crap all along the road to boot.