Hmmm… Blackbeard is just being a pirate. They share the Will of D, both know how to have fun, both believe in dreams, both following the same dream. The difference? One is the darker side of pirateing and one is the lighter. Now Luffy represent freedom, yet is consider evil to the World Government. Blackbeard is seeking to join the Shichibukai, which would mean the WG would see him as an ally (not evil). Even their DF powers are a contrast, BB's is overpowering and Luffy's is overpowered (lol).
But anyway pirates are criminals, criminals are villians, villians are evil. So to answer the question "Is BB evil" you must define when a pirate stops being "good".