Your heart is in the right place, but you're a bit misguided and nieve on how powerful speech, can be. As counter-intuitive as that sounds, we only need to look at history to see examples of how positive and negative speech has been able to influence millions. For example, Gandhi & MLK both had hugely positive effects on the masses. So much so they were labeled as threats to the country. The FBI went so far as to create an agenda against MLK which eventually lead to his assignation.

Another example is the Rwanda genocide of 1994. The history of the Hutu and Tutsis goes back long ways, but a critical part of the event was how fast people across the country turned on their life-long neighbors and began slaughtering them by the hundreds of thousands. This was only possible because of the hate-speech from the Nationalist Hutus building up to that moment and spread through the radio calling for the murder of all Tutsis. There's a lot of similarities to that event and what we see now around the world with white nationalist. One only needs to look at any conservative media, and you will see hundreds or thousands of people rallying around calls to kill all liberals, anarchist, Blacks, Mexicans. Jews, LGBT, etc.

I don't put Shapiro into the category of hate-speech, he a little more level headed and scientific about how he approaches what he thinks. Nor do I agree with the methods being used by the counter-protestors of late but there is a powerful statement in their willingness to stand up and push back when threatened, beaten, and killed. And yes, that's what has been going on from the far right. Who, have thus far carried out more terrorist attacks than Muslim extremist and liberal extremist combined. So, it's not unexpected to see the violence from the counter-protest. Is it right? Well seeing live streams from Luke have proven that the violence, is as Trump has said, "on both sides."

Should they try and shut down his speech? No. I agree with you that it gives validity and power to his position. Should they remain quiet and pretend what is happening all around them "doesn't matter?" No, because the reality is, people are influenced into committing acts of violence from the rhetoric. Standing up to it shows strength, builds a community of like-minded persons and gives them experience in those violent situations that very well may escalate as shown all throughout history.
http://www.hawaii.edu/powerkills/NOTE1.HTM

What's interesting to see is how people are reacting to the counter-protestors calling them anti-free speech while condoning the anti-free speech actions of the city council and police.