That’s certainly a shrewd tactic. I can’t justify it though.
Catholicism might be okay with it: “Sure, bring your fertility symbols and your winter solstice trees. We’ll incorporate them as Easter bunnies and eggs, and Christmas trees. Anything to get you to join our religion.”
Diluting a lie doesn’t make it any less a lie. (”Muslims and Christians both worship the same god.” - G. W. Bush) And I’m not convinced that any (or the most) good can come from pretending a lie isn’t a lie - even in the area of politics/AGW. Maybe I’m wrong?
2. I wouldn't lie about having the differences - just not argue them, in order to show that together we can accomplish the "common good" - solving the problem their "religion" supposedly tries to solve with the practical methods and tools that are far superior for both people and the environment than the "solutions" their "teachers" told them to be necessary as the only ones capable of doing the job / "saving" the planet.
Eventually, the hope would be that they would wise up as a result (they don't even have to give up their love for the environment, if that is what it really was in the first place, rather than fear of "environmental disaster") but, if not — fine, the rest of us (and they, too) would not have to bear the burdens and the expense of the progressive "environmental solutions" (i.e., transfer of capital from productive sources to their own pockets) which is the only reason the progressives are in this game, for as long as they can take it.
Deny the progressive "thought leaders" the means to financially benefit from the "AGW / man-made climate change" hoax and you'll see how fast it will disappear from the news in favour of some other necessity or disaster du jour - investing in "infrastructure" (like light rail) is usually convincing enough for enough people to vote for it.