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Shall I practice willful ignorance of the metaphor here and ask why you only make buildings in one color?
You are seeing/hearing language change right in front of you. Like watching "collectable" replace "collectible." That one used to really bother me, but conventions change, and that is life. We all know what green means now. We are getting used to what carbon means.
Two more important points:
1. No one can "make you" feel guilty. Is there something you feel bad about?
2. Regardless of how right you may be, you are not in control of the way other people use the word carbon. You can only control your own use of the word. If you start adding the 'dioxide' back in, maybe other people will too. Or maybe they will just give you weird looks, like the looks I give people who insist on pronouncing 'Feng Shui' as though they were native speakers of Mandarin. (Do you do that too???)
Choose your battles carefully, or you're going to be a very unhappy person.