Insisting people pass on the freedoms that they benefited from to other users, is not extremism. You have a chip on your shoulder.
You say that copyleft removes your freedom to choose to distribute a program as proprietary software. This is correct, but you portray it highly disingenuously, like it's an equally weighted choice.
Generally, freedom has the most influence when its recipients are those at a lower position of power. The power of the software vendor is to have full control over the usage of the program, ostensibly either to provide a better UX (which is dubious), to exercise their IP (an ethical landmine), to benefit from unsustainable per-unit business models that ignore software's intrinsically anti-rivalrous, non-scarce and intangible nature, or other reasons.
Let us see how the user is affected. And keep in mind, all programmers are users. Programmers will be using other people's software at dramatically higher quantities than they will ever write anything individually. As such, user freedom is of paramount importance to them.
Now, for a certain amount of convenience on part of the vendor, the user is put in a position where they cannot a) run the program for all purposes that they may desire to use it, b) study and change it to adjust it to their needs, c) share it with friends, neighbors and acquaintances and d) enrich their community by sharing modified copies. In other words, they get software without most of the benefits that actually comes with having things be software in the first place.
As such, the users lose individual and collective control for the benefit of the vendor, but at a deadweight loss for everyone else. Because, when the software leaves the vendor into another person's machine, how it's used is in no natural sense of any interest to them. Not anymore than a chef is interested in how other people use their recipe. This has been accepted as the first-sale doctrine by courts across the world.
I therefore conclude that user freedom should be given at all times where the software is user-facing.