How much should a new gas boiler cost?

Appetizing argumentation.

But why stop at the unborn and children?

What do you conclude from the fact that the CO2 footprint of adults is probably even higher? And that of adults in first-world countries even higher? And then significantly (!) higher again among the wealthy in these countries?

That definitely calls for building a mausoleum.

I believe what Rick wants to point out is that we cannot argue purely scientifically in the climate debate. Because if we did, in order to maintain even a minimum quality of life, we would have to live in tiny rooms in apartment buildings. Single-family homes, children, new cars, travel, using the internet in leisure time, air conditioning, consumption goods in general—all are potentially harmful to the environment. We would have to reduce ourselves to a minimum.
But of course no one wants that, so the debate is naturally also conducted morally and ethically. And here the question arises of who wants to and, above all, may set binding rules for the entire German population. Hence also the extreme example with children.
One person generally strives for the greatest possible freedom in their own behavior and thinking, the other considers certain prohibitions completely legitimate and sensible. Now person 2 brings up the scientific arguments but ignores the moral question. Person 1 argues morally but possibly neglects the scientific side.
Furthermore, especially in Germany, comes the monetary aspect. We try to steer things through money. Unfortunately, in a way that makes unwanted behaviors very expensive rather than making the desired behaviors financially attractive.
In particular, people with little money often simply cannot afford the rather expensive initial investment (and now we are on the topic). How is the retired couple from the working class supposed to afford switching to a heat pump? So they continue to heat expensively with oil, because the ~50k simply isn’t there.
Do we now want to take their house away because younger people have a better claim to the house and would also modernize it? After the old couple perhaps built and worked hard for the house themselves?

The whole discussion involves incredibly complex issues that require a comprehensive view and solution. So far, I have seen neither in science nor in politics.

Science has known exactly what to do for 40 years. Solutions for social compensation also exist. Politics just doesn't listen. And please, let us take care of ourselves first before we shift our hesitation onto old, poor people in [zu großen Häusern]!

Exactly. We agree on that. Everyone should first start with themselves and ask what they are doing, want to do, and what they are willing to give up. And then you have to accept that others have different priorities (even though their footprint might already be smaller). Regarding social compensation, I have not yet seen a globally viable concept. We only have limited influence on that, and it is getting smaller. We can only make a contribution within our own scope. Unfortunately, it plays almost no role as long as Asia, India, and America do not get on board.

More on-topic: besides air-to-water heat pumps, you can also possibly use a brine-to-water heat pump in the former mining area, e.g. with the help of a [Ringgrabenkollektor]. Admittedly, this is mostly difficult (and often impossible) in existing buildings, but in this case, you can do quite a bit yourself to reduce the overall costs.