I don't believe this is true. The microwave uses simple Radio Frequency energy to make water molecules warm. It does not add anything to the food. Cooking food can make it less healthy, and I think if you looked carefully at all food cooking, you will find positives and negatives. I imagine that a barbecue adds many more carcinogens to food, including burnt oil, smoke, soot etc. But I think this sort of thing is normal, and I love the taste of a good barbecue!

not only microwave can make you an eater canceragenic nowadays, that's why stop worrying about this kind of things.

yes as Neil says, grilling outdoors can create carcinogens on food in certain conditions. But that fact does not stop us from cooking out at least some times