"My professional opinion is that we should turn everything off and let nature take its course."

In fact, until this month, I don't remember ever having been asked for a professional opinion on anything at all.

In my professional opinion, this is going to come to a head tonight.

This is not to say, of course, that professional opinions are always correct.

"In your professional opinion, would you consider such a comparison significant?"

"The curator will meet us in a little over an hour, so take a look at this and give me your professional opinion."

Is this a professional opinion or just a personal insult?

His answers may not represent the full range of professional opinion.

That was his professional opinion and he could see no reason to doubt it.

I knew he couldn't resist being asked his professional opinion.