I'm in agreement Dave.

I try to think about this kind of thing as I would when dealing with children.

When telling a child that they should/should not do something it is generally more effective to give an explanation of why than just to issue an order. In the main the child is more prepared to heed the advice if given a reason why and less inclined to get sulky or disobedient and go against what is asked.

Same with criticism. If I don't like something I try to work out why. That way it isn't just a gut reaction against something new and unfamiliar and I can, to some degree, justify my opinion to others. That generally leads to more accord when I can agree to disagree on a subject. IMO it is certainly more respectful than just baldly stating that I don't like something or 'it's crap' which tends to come across as 'if you like it you must be stupid' in a lot of cases.