To put it another way, this whole line reminds me of the same thing with charity. You have a person with money who supports a charitable cause, and they give a lot of money to it, and someone responds, "..but you still have possessions X, Y, and Z! if you really supported the charity you'd donate more!". But it's a line of attack that the person donating to charity can never win: no matter how much they give, they can still be attacked for owning things, unless they donate to the point that they're homeless in the streets scrounging for food from trash cans.
If the argument was that Al Gore had a particularly high level of environmental impact relative to his wealth and other factors worthy of consideration (his job, where he lives, etc), then that would absolutely be grounds for charges of hypocrisy. But otherwise what you're really complaining about is wealth inequality, and doing the unwinnable argument, "If Person X really cared about Issue Y, then they'd give even more than they currently do!" - regardless of what that level of giving is.