Yep. It's possible, but not always. Still, it's possible more often than many would suggest. The big mistake most people make is thinking that having impenetrable logic behind your argument is enough.
For some people, having a rock-solid argument is all that's needed, but it requires them to have an open, mature mind and we all know that's not something you'll find often from random strangers online.
Those who have closed minds require more work. They must be eased into a less combative way of thinking. If they see you as their opponent, they won't give ground no matter how solid your argument is. By approaching them with intellectual curiosity, and re-framing an argument as an earnest search for the truth, you can make them less defensive and more willing to listen to you. This means putting on a less stalwart front, showing that you have doubts, or acknowledging strengths in the other person's argument, even if they might weaken your own argument. You want to show them that you won't pounce on them the moment they let their guard down. Once their minds are open and they're willing to join you in seeking the truth, then your arguments can have an effect.
This has led to some very productive discussions for me, even in the Youtube comments section.
Of course, there are those who actually don't want to have a discussion. They're there just to stir things up, and won't engage with you, because they don't want to know the truth, they just want everyone watching them to react a certain way. Trolls, basically. At the very least, they'll leave you alone if you don't come across as being the reactive sort.
