Why do you think you have a right to attack others opinions?

(Take this question as an example) In a question about which is sweeter; brown sugar or palm sugar?

Mr.A said: palm sugar. Because…..XXXXX…..

Then Ms.B says: No,Mr A is wrong. It’s brown sugar…XXXXX….
and so on.

Ms.B could have her opinion without justifying Mr.A’s opinion with her own opinion but she didn’t. She has provoked something she can avoid. Then they both ended up in unhealthy competitive system.

So you have figured it out that this question is for people who are like Ms.B
So why you do think you have a right to attack or it’s necessary for you to kill others opinions? Don’t you think each person can have his/her own opinion toward an issue? An urge to dominate other people maybe?