Just to start things off, you do realize that firing him would appear to be illegal? At least, assuming there are no arcane reasons why California's laws do not apply here:

http://www.dir.ca.gov/dlse/HowToFileLinkCodeSections.htm

Labor Code section 1101

Protects employees who engage or participate in politics or who become candidates for public office. An employer may not make, adopt, or enforce any rule, regulation or policy that forbids, controls, directs or tends to direct the political activities or affiliations of employees.

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On to the philosophical point, why not go back to Karl Popper? If we look carefully, though, we see that he predicated this intolerance of intolerance on protection from violence. He was not afraid of any intolerance of words so much as those who would close their ears and swing their fists. So it was more a sort of right of self defense against anyone who would use violence and not persuasion: https://en.wikipedia.org/wiki/Karl_Popper

Note how his argument is predicated on the need to protect people from violence. Unless that is a need there simply isn't a reason to ban things.

But wait, the Trump supporters have been violent, right? That was all over the news, I'm sure. Everyone saw that. So we have good reason to suppress a violent movement now, do we not? Well, maybe, if we didn't see this:

https://www.youtube.com/watch?time_continue=2&v=5IuJGHuIkzY

Wait, no, that guy made ACORN videos. Can't be trusted! Must be fake! But, umm, we've seen that lady before. At about 17:40 in this video, you see the same person: https://www.youtube.com/watch?v=3uMzYaO2syE

You can even see a tiny mole on her chest in the same place. She's there, blocking the road and doing everything possible to delay the cops from clearing that out. But how do we know who she really works for? Well, what do you know, she's listed on the FEC website, they can tell us! (We can trust the FEC... right?)

https://beta.fec.gov/data/disbursements/?two_year_transactio...

Spender	Recipient	State	Purpose	Disbursement date	Amount
STAND UP FOR OHIO PAC	RODRIGUEZ, ZULEMA	AZ	REIMBURSEMENT FOR T-SHIRT PRINTING	06-10-2016	$320.00
STAND UP FOR OHIO PAC	RODRIGUEZ, ZULEMA	AZ	POLITICAL CONSULTING FEE	06-01-2016	$17,500.00
MOVEON.ORG POLITICAL ACTION	ZULEMA RODRIGUEZ	AZ	TRAVEL EXP	05-24-2016	$1,108.97
MOVEON.ORG POLITICAL ACTION	RODRIGUEZ, ZULEMA	AZ	REIMBURSEMENT	05-24-2016	$1,108.97
HILLARY FOR AMERICA	RODRIGUEZ, ZULEMA	AZ	PHONE	02-29-2016	$30.00
HILLARY FOR AMERICA	RODRIGUEZ, ZULEMA	AZ	PAYROLL	02-29-2016	$1,610.24

In other news, she brags about her work at other protests where you may have seen pictures of a very injured cop. Lest we forget, remember that they also framed Sanders supporters for some of this stuff.

Given that this violence was deliberate, do you also, based on that philosophic reasoning, support the same censure of anyone who supports Hillary? It would appear to be the logical conclusion to your argument given the campaign's deliberate violence, would it not?

For the record, I find Trump a deplorable candidate. But the very idea that people would attempt to force us into a one party system by means of organized violence or excommunication from society won't sit well with many people. Especially not when it also appears that people are also herein advocating an action that appears to be flat-out illegal!