I hate to rain on your parade, but lots of people have tried that strategy and it hasn't worked yet.
1. I hate to rain on your parade, but your plans are all wrong.
2. I'm sorry to rain on your parade, but you're not allowed to have alcohol on the premises./I'm sorry to rain on your parade, but you're not allowed to have food or drinks in the theater.
I hate to rain on your parade, but lots of people have tried that strategy and it hasn't worked yet.