Non-citizens in Germany have no free speech rights period. You get banned and deported even for making lectures about unfavorable topics, as it seems.

That's quite different from protesting, since you're not making anyone listen to you. Lecture/conference is an offer, that Germans and others may take out of their own interest to learn about what you have to say.

That also infringes on the German citizens, because you're attempting to limit them from what they may choose to learn.

> Non-citizens in Germany have no free speech rights period. You get banned and deported even for making lectures about unfavorable topics, as it seems.

No, the right to utter your opinion in Germany applies to everyone, not only Germans. The constitution has two categories of people, Germans and Everyone, some rights apply only to Germans, some to Everyone. The right to assembly and public protests is one just for Germans, the right to freely utter your opinion applies to everyone.

However, that right isn't what Americans think when they hear "free speech" (which is why I avoided the term earlier): There are far more limits to it, like the criminalization of giving offense ("Beleidigung"), promoting or misinforming about Nazism and other crimes against humanity ("Volksverhetzung"), deadnaming, speaking ill of foreign heads of state or domestic politicians, and condoning criminal acts. Also, only an opinion is protected, not a statement of fact, no matter if it is right or wrong. For example, a journalist was fined for writing about chancellor Schroeder dying his hair. The court didn't even try to find out if it was right or wrong, it was a statement of fact, so unprotected, and it was offensive to Schroeder, so an offense ("Beleidigung").

So in conclusion you are kind of right in that there is actually no freedom of speech for anyone in Germany, not even Germans, that right simply doesn't exist. Its just that foreigners are treated the same as Germans, there is no difference in rights there.