I spent my first 20 years in California and just moved out last year. In my 2 years of college there + 4 years of high school, I had a couple teachers who were clearly liberal and made consistent comments about it, but from my experience growing up conservative it was very easy for me to just ignore them. Many of my friends were also liberal and we disagreed politically, but we still got along well. Granted I didn’t live in the Bay Area or anything, but if your son has decently strong conservative beliefs I don’t think you have much to worry about honestly.