| The only thing I can think of to explain their behaviour is some weird need to maintain control over you with disapproval.
And the worst part is that it might even be subconscious. Parents are people too, and we all have our insecurities. It just sucks badly if you let an insecurity screw up a valuable relationship so you can feel better.
Instead of right out accusing them of behaving badly, I'd ask them what on earth they thought they were doing. If a satisfactory explanation isn't forthcoming, I'd then start talking about behaviour and your place as an adult child (who has relationships that they can't control) in their lives. | 
