The few people who do practice Scientology think of it as a religion, but it is considered a cult in many parts of the world, including Germany, which is why Adidas, a German sports clothing manufacturer, will cancel any sponsorship deal they have with a player if it turns out he has anything to do with the teachings and ideas of Ron L. Hubbard.
Der Spiegel got hold of a contract between a Bayern Munich footballer and Adidas from 2008, in which it is mentioned that the player had to assure he has nothing to do with any organization or associations which represents the teachings of Ron L. Hubbard.
Scientology isn’t the only thing that Adidas worries about: A player shouldn’t be connected to any organization monitored (knowingly) by an intelligence agency, and any drug use or something of the sort is also going to lead to the cancellation of the sponsorship deal.1
From wikipedia: Since 1997 Germany has considered Scientology to be in conflict with the principles of the nation’s constitution. It is seen as an anticonstitutional sect and a new version of political extremism and because there is “evidence for intentions against the free democratic basic order” it is observed by the Federal Office for the Protection of the Constitution.
Adidas have contracts with players from all over the world, including countries in which Scientology is a religion and not a cult. However, Adidas aren’t an employer: They’re paying a player for use of his image, and if that image reflects badly on the company, they reserve the right to severe their ties with him.