There is a difference between being critical and being negative. Thinking critically is an important part of Wesleyan theology as we encourage people to use reason when thinking about things as part of Our Theological Task. I'm guessing when asking people to think critically, we're not asking them to complain or hate on everything.
This goes beyond theology and into every aspect of life; politics, books, movies, work, education, church, etc. Critical thinking is more than simply saying something is "good" or "bad," that you like it or don't. Critical thinking answers the question of why you like something or not.
So tell us, how do you give critical feedback without being negative? Do you receive critical feedback well?