How to deal with strong PD?

[Sombre]

It hasn't stopped you, it's just delayed you. They spent loads of money on PD which will be useless when you later attack with your superior force and roll over the PD like it isn't there.

Unless they have forces/research to match yours AND the PD all over the place as well, in which case they just had a better early game than you - find an ally and double team them.