Presumably we need more air conditioners precisely because there are currently people without them..? I think the guy you're responding to believes there's a need for more AC to prevent exactly what you're describing.
And re; what you're describing, if you have an AC you (generally) don't need more AC's, that'd be pretty pointless. AC units aren't a thing that makes any sense to hoard away, so the future you're imagining where people in "mansions in the desert" somehow have all the AC and everyone else is just "boiling" away doesn't really seem like a realistic concern. Especially so if people agree that building more AC's will help.
And re; what you're describing, if you have an AC you (generally) don't need more AC's, that'd be pretty pointless. AC units aren't a thing that makes any sense to hoard away, so the future you're imagining where people in "mansions in the desert" somehow have all the AC and everyone else is just "boiling" away doesn't really seem like a realistic concern. Especially so if people agree that building more AC's will help.