If you've ever had an opinion, then you've spent time trying to prove it true. If this has ever occurred in your life, than you've divulged in one of the most pointless human acts that's ever existed, which everyone loves to claim is important. In fact, people can't walk outside anymore without being bombarded with people shouting at them, holding their opinion as gospel and damning anyone who disagrees with it.
People hold up traffic, break shit in the streets, and ruin their own happiness because their opinion didn't change their enemies minds when they were quiet. But the thing is, once someone has consumed the facts of a situation and made their mind, changing that opinion is almost impossible. Opinions might change over time, but that comes from years of conflicting emotions with their own thoughts, but most people are perfectly content with their own mindset, so they won't ever change. Do you believe that shouting at this man who has made his mind will change anything? It's pointless.
I guess the best justification you can make for opinions is to influence the people who haven't already formed one, but these people are usually children and idiots, and I don't know why you'd even want them associated with you. I'm not saying opinions aren't important, they're the basis of our society, I'd just stop investing so much time in doing something so pointless.
TLDR: Your opinion cannot be forced upon others, don't waste your time and enjoy life instead.