If you demand that I respect your opinion, I immediately don't respect you.
I can respect you while disrespecting your opinion rather easily. I can respect your opinion while disrespecting you fairly easily. Respect for a good person who voices a stupid opinion from time to time isn't hard to achieve. Respect for a valid insight given by a broken clock who happens to be right twice a day isn't hard.
Demanding that your opinion be respected is a paradoxical demand. If you demand that I must necessarily respect your opinion you're actually demanding that I disrespect you as a human being. You're demanding that I treat you like a child and respect every stupid thing that comes out of your mouth in order to protect your self-image. At the same time, an expectation that I should respect you as a human being would force me to speak truth to your opinion and disrespect any opinion that I find to be faulty or downright wrong.
Do you want me to respect you as a human being; or, do you want me to respect your opinion? Oftentimes I can't do both. Nobody can realistically do both on a regular basis.