Implementing a policy as a private (read; quasi private) business is one thing. But freezing assets based on an ideological preference that is not spelled out contractually is a breach of contract.
They are doing it because they know that the Obama (non)justice department has their back. They're acting as a harassment arm of the regime. Expect more of this kind of thing to be done even more flagrantly as economic fascism takes hold.
I would look for conservative think tanks, media, or individuals to be similarly harassed.