Normally, when I disagree with others, I don't reflect it on them too much, but when they insist that my ideas are ridiculous, then things change. arrogance is a really bad feeling. I may be thinking too selfishly, but it makes the most sense to defend my own opinion to a certain extent rather than insulting the opinions of others.
If not sharing an opinion or personal thought with others makes you feel that they are full of crap, then you are a selfish person.