Remember, there are very powerful forces at work out there to make environmental activists look like loonies and eccentrics in order to discredit them. It doesn't surprise me that the mainstream look down on them having been appeased into non-action by propaganda. If you go to such an event you'll probably be impressed and forever changed by how well educated and informed the activists are, and by how the media have falsely portrayed them.
I think you misunderstand completely why people tend to dislike environmental activists.
There may be mainstream media propaganda against such folks. I know many who would argue the opposite. But any influence the media has over the issue pales in comparison to simply (1) knowing what the stereotype of an environmentalist is (save trees, save animals, don't hunt, don't burn, etc.) and (2) seeing some of the more outrageous-looking activities of activists. By outrageous-looking, I'm not talking about ELF. I'm talking about folks chaining themselves to trees and such. Believe me, going to the events to try to understand activists stands just as good a chance of making the situation worse, should many people realize that their beliefs about environmental activists are pretty reasonably accurate. Why? Because the motives of the activists just flat don't matter to most. It's their actions, and the immediate impact those actions have on others (and the uncaring way such actions are perceived as being done) that matter.
People can get on board with clean air and water. When you start stepping on their lives to "save the planet" from alleged ills that they're expected to take university-level classes to fully understand (never mind prove,) they're not exactly going to be very welcoming.
In addition, the mindset that animal rights or environmental care (again, let's exclude actual overt pollution, here) trumps individual liberties and property rights is a totally alien one to a broad spectrum of society, at least in the U.S. So when someone sees folks attempting to interfere with their normal activities--logging, mining, developing land, any of a number of "environmentally-impacting" jobs--they'll first wonder what such people are smoking. But that quickly turns to rage when they see these (to their mind) lunatics actually impacting their legitimate livelihood and/or desires. Were such confrontations to start with a conversation, there would probably be no change, but at least a first step would be made, with further steps to come later. And the deep-seated backlash of people who feel you're throwing slanted theories and alien emotions at them while trying to coerce them to act upon those theories and emotions could be avoided.
It's not clear to me that you really have a deep understanding of environmentalism. Let's review some of your opinions, and get educated.