Question (should PO to participate retrospective meeting)?

should PO similar to other Scrum Team members attend and participate actively in discussions in the retrospective meeting?

I myself think that he/she must attend and support the improvment process by sharing his/her feedbacks and geting ideas from disscusions.

But I have read recently that is controversal and the presence of PO might have impact on Dev. memebers' safety feeling (hidden gun effect) ?

What is your oponion/ experience from project? pros / contras?

Mehdi