Why don't testers and programmers like each other? [closed]

Question

During my career as a programmer I've seen various programmers and testers, and many of them didn't/don't like each other. I mean, programmers think that the job of a tester is not a "real" job, and testers think that programmers are too "proud".

Is this the right decision made by me, why is it, and what can we do to avoid these kind problems?