Unfortunately, banks are private company and they don't have any obligation to serve anyone or justify why they don't want to.
Exactly. Unfortunately we need them more than they need us, hence they have the power. Pretty ordinary way to treat customers though, especially customers who are doing nothing illegal or immoral and just happen to be interested in bitcoin. I had a similar experience with an Australian bank which prevented my transaction (transfer to an exchange) and then refused to even tell me why.
This highlights why we need this whole bitcoin experiment to live up to its promise - it is the only way we can kill these pr!cks running the show. Best part is I think we will succeed, unless the banks convince the regulators to clamp down...