I'll take a strawman SJW anytime over Randroids, which is the other side of the Internet.
This all suggests a very peculiar mindset to me. I can't quite fathom how you could find someone challenging your beliefs in a polite manner to be insufficient to get you to actually think about your position, whereas someone challenging your beliefs in an incredibly rude and aggressive manner would actually succeed. While I don't question that what you're saying is true for you, I really can't see this as being applicable to many people. For myself I would say the complete opposite would be the case. If someone is polite and reasonable with me then it puts me in the mindset to take the time to actually listen to them and be more agreeable to them.
Regardless of whether what you're saying here is actually true, how many people are like that? Are most people actually reasonable, or do they simply fancy themselves reasonable?
Even in this forum, I have often seen discussion with 'reasonable' people go nowhere until it finally devolves into name-calling because the 'reasonable' people simply refuse to consider the other side seriously and keep repeating the same 'reasonable' arguments over and over in various guises. And this also happens in situations where the 'reasonable' people are not in a good position to actually fully understand the issue being discussed - they're just being stubborn like any unreasonable people. Maybe they're just more articulate and polite about it compared to the average YouTube debater.
Of course, there's the time and space for 'civil discourse', but expecting the Internet to be sterilised to become such a space is pointless and counter-productive. Civil discourse can become stagnant or even exclusive. The average person is often completely locked out of meaningful civil discourse that is happening on a national level, for example. Even if you consider peaceful protest to be part of civil discourse (some societies don't - it's still considered disorderly behaviour for the inconvenience that it can cause), it can be and has been completely ignored. While explosive incidents can ultimately be counterproductive, they are also good at forcing people to pay attention, which is basically the first step in creating any change.
And if we're talking about the Internet, what space can possibly be safer for explosive interaction? There's little chance for violence or destruction to happen as a result. Moreover, even if such interaction does not win anyone who is involved over, it becomes part of a larger political struggle between one side and another, and whichever side struggles most vigorously in the end has a better chance of succeeding.
SJWs get attention. Some people obviously react badly, but time will tell whether they will actually succeed in setting the agenda for discourse for the coming generation. They may well succeed.