No comrades of mine would see guest workers or immigrants as a threat. I wouldn't join a union that didn't stick up for all workers, regardless of their citizenship status.

Maybe we have different perspectives on how popular the anti-immigrant position is in tech (and how many neo-reactionary/dark enlightenment dipshits there are), I guess I'd just ask that you keep an open mind about this and make a decision if and when workers approach you to join a union. I certainly wouldn't knock you for opposing a group that doesn't have your interests at heart, but the union I want to form would take solidarity seriously and would explicitly go to bat for women, people of color, lgbtqia people, disabled people, and immigrants.