No one infringed on his right to free speech.
The government wasn’t involved so his 1A rights are intact.
One would have to read his employment contract to make any allegations about his use of school time/equip to pursue his political free speech ... so that’s a side issue.
Free speech counters free speech.
Free speech doesn’t mean the right to zero consequences. (This is where Tim Robbins was wrong).
To a liberal, it’s exercising free speech when he defecates on a conservative’s front porch.
When a conservative offers up a differing viewpoint on an issue, it’s hate speech.
These people don’t have even a rudimentary understanding of what “free speech” really means in the Constitution.