Earlier quoted context omitted.
What "arguments like this one"? It isn't an argument at all, it's just pointing out some actual facts. If your slippery slope argument can't withstand a simple statement that something is at the top of the slope, it's not much good.
Authoritarianism rarely happens overnight, it happens one step at a time and at every step the useful idiots [0] exclaim "It's just one step! What's the big deal? Stop overreacting!". Next thing you know you've walked 100 miles and it's too late to turn back. [0] https://en.wikipedia.org/wiki/Useful_idiot
The slippery slope argument says that open source software is a stepping stone to a world where all commercial activity is banned. Should we therefore oppose open source software?