There have been issues with pre-order bonuses before. But it has been minor stuff like skins and weapons. Even though this is unacceptable for us, they still give retailers their own pre-order bonuses that they take out of the game and make only for them. Now with pre-order bonuses including DLC, it's becoming a practice that's against the consumer.
A game that you don't pre-order is just as good or bad a few weeks after it has been released. The only reason i really buy games on day 1 is to support a certain developer that i like. But that doesn't happen so often and we should actually support games that have no incentives on pre-ordered games.
I usually just wait to buy games, because i don't support this. Consumers should be able to go where they want with everything. Unfortunately it has become a bad business practice during the last generation of games. Vote with your wallet and don't support this kind of thing and let them know this stuff will not stand.