1. The bike lane is not a right-turn lane for cars.
2. Unlike cars, bikes have a "stall speed," below which point they became unstable and difficult to steer precisely. So if traffic patterns don't let a bike stay comfortably above a certain minimum speed -- depending on the bike, the rider, and the road conditions, it's something around 4 mph -- things get less safe, not more so. Best option: Don't force bikes to go that slowly. Next-best option: If they have to slow down that much, give them a little extra room.