If you express something, it should have a constructive purpose.

I feel like trying to make any expression constructive is one of those 'nice in theory' but also 'not a thing that has ever or will ever be done by any human being, because it's an insane inhumane thing to practice' ideals.

You cannot make every expression of opinion constructive. Take the case of this post. There is no need for constructive criticism or expression here, because the people doing this are not doing it out of good will. It then follows that any use of energy to provide that constructive expression is an unnecessary waste of goodwill.