Some hiring managers might like their tweets and show support in their personal time but when it comes down to actually hiring them they'll wonder if this person will be disruptive and constantly bring their personal activist life into the workplace, making other employees lives difficult, lack self control and say the wrong thing to customers, etc.
> they'll wonder if this person will be disruptive and constantly bring their personal activist life into the workplace
Corporations very often take stance on political issues, also when interacting with their own employees. For example all the pride events, which Google is known for. So it's not like these employees started bringing politics to the office, but rather they dared to have their own opinion that the system didn't like.
If you went to Google campuses and protested gay marriage rights then you probably would be fired too.
I dont care about X why do I have to deal with your 'protest'?
If the protesters camped in an execs office for pride and refused to leave, they'd likely also get arrested. It's just that there wouldn't be such a protest in the first place.