I’m gradually developing a loathing for conservationists. Reading about these people blocking progress on the fossil-fuel phase-out is very grating. I’m sure they’re also opposed to nuclear power and other good things like happy children.
Regardless, there is probably a middle ground for the lamps between "widespread use" and "extinction". It's not great that they are inefficient, but they are certainly historical, and the emissions from a few thousand gas lamps are a drop in the bucket for Berlin and the world.
I would argue that the cultural, historical and educational value of the lamps should be given weight against the downsides and preserved to some extent.
Again, surely a compromise could be found -- replace, say, 98% of the gas lamps, but leave 2% functioning in a special historic district.
With smart leadership and marketing, such historic areas can drive considerable tourist and economic activity as well.