No, people shouldn't be downvoting comments just because they disagree with you. However, if you say something that goes against the grain, you're going to get

No, people shouldn't be downvoting comments just because they disagree with you. However, if you say something that goes against the grain, you're going to get downvoted every now and then anyway. It helps to develop a thick skin, or better yet, try to ignore comment scores altogether.