It sounds like there is no fallacy. How has the statement been "unduly extended"? A statement was made, and evidence was provided to back it up. That sounds very duly extended.
You have a discussion where the initial assumption being accepted as an axiom is "We should try to reduce climate change by reducing fossil fuel consumption," and the discussion includes "We should convert to electric and/or bikes." This is the point being debated, "We should convert to electric and/or bikes."
Given the statement which is accepted as an axiom by those involved in the discussion (that global warming is bad and we should reduce fossil fuel usage to reduce global warming), "We should convert to electric and/or bikes" (roughly equivalent to saying "We should stop using vehicles which consume fossil fuels") is a fine point. However, "We should stop using wireless communications, as they consume almost as much fossil fuel" is an equally valid point. And, all other things being equal, you might as well accept both or reject both equally.
Therefor, it is perfectly reasonable to insist that the two proposals have the same outcome, that either they are accepted or rejected together as one. There is nothing wrong with this, and there is no fallacy so far. There is no logical necessity to demand that the proposals have the same fate, but there also is no problem with making that demand either; it is neither here nor there.
If you desire to have the two treated differently, then what you must do is provide a reason that they should be treated so. Remember, I said "All other things being equal," so provide some logic showing that they are not equal.
Further debate may well cause the other person you speak of to rely on logical fallacies to support their argument, but merely stating that "If A is roughly equal to B, then we should accept or reject them together" (ie: "Transportation and communication are roughly equal fossil fuel users, therefore we should accept or reject them together") is not a fallacy. Indeed, the onus of burden is on you to suggest why two equal things should be treated differently.
There are plenty of things that the debater you mention could have said which would change the answer, but we cannot assume anything and must go only with what information you have provided. So the answer is "No solution - there is no logical fallacy therefore no name to provide."