My Opinion Isn't (A) Right

I thought the discussion in class had some really... eye-opening points or topics that needed to be addressed. I think that Noah had a fine point in bringing up the pursuit to happiness, that if he wanted to do heroine and become a prostitute, he should be able do so to because it's his body. And I certainly agree; if someone wants to damage his body by doing drugs, then by all means, let him self implode. That's his decision and his doing. The only problem comes when he becomes a danger to others. I also have a problem with drug users when they rush into the hospital with drug problems and can't cover the medical costs, so average citizens like my parents have to pay for them with taxes. It's like we're paying for this guy to do drugs. This will sound harsh, but just let the guy go, let him ruin himself and die if he accidentally does so. He knows what he's doing; he's made his choice. It's his fault for doing that to himself.
But this is getting way off topic. Getting back to the right to our opinion (or lack there of), I agree that just saying, "I have the right to my opinion" is just a person's last shot to fire, his last line because he has no other defense. He's just saying that to shut down the argument, to make up for the fact that he has no other come back, no other evidence to support his opinion.
But on the other hand, an opinion is just a view or judgment formed about something, not necessarily based on fact or knowledge. So why can't everyone have their own opinion? their own judgment? That's one of our rights as human beings. Now some countries can and cannot allow their citizens to express their judgment out loud, but people have them nonetheless, in their minds. So doesn't that let me have a right to my own opinion? If you say that I can't because I have to back it up with knowledge or evidence, I can say that I don't need to because opinions don't need evidence to support them. It's just an opinion, not some crazy fact I made up that I'm trying to make everyone believe. My opinion is my own perspective, stance, viewpoint, whatever you want to call it. But it's still mine, and I can think what I want to think. I don't need facts to support what I'm thinking, what my opinion is. "I think yellow is the best color." That's my opinion. Evidence? "It's a bright, happy color that is reminiscent of nice things like flowers and the sun." But that's still my opinion. A lot of people probably don't think that 1) yellow is a happy color, 2) that flowers and the sun are nice things. So even the evidence, it seems like, is just your opinion too. Your opinions support your opinion. Because opinions aren't based or supported by facts or actual knowledge. Why do you think they're called opinions?
I think that it's acceptable to say "I have the right to my own opinion" after you try to show your point, make your case. But if the person retaliates and shuts you down saying "No, that's wrong", then there's no point arguing because that person's close-minded and isn't open to what you're saying, because that person saying that my opinion is wrong is his opinion. He can't prove that my judgment not based on fact is wrong because there are no facts to check. So we both have opinions; he's just less open to mine than I am to his.