Trigger: tell them your environmentism is a core pagan belief, and as such you are entitled to practice it whenever and wherever you like, under your country's freedom of religion statute. Christian fuckers aren't the only ones with rights, and anyone is entitled to practice what they like.
If they don't like that, then tell them that you wish good karma on them, because unlike Christians, pagans never curse.
That'll fuck them up for a bit.
Then when they start their shit on you again, start wearing pentagrams and other pagan symbols. If they keep harassing you, tell them you'll report them to the Anti Discrimination Branch (or whatever you call it).