A green handle of "communist_" does not inspire automatic belief that you truly had friends at Mozilla Corporation or know of any such tweets.
Again, if you mean the six Mozilla Foundation employees who tweeted against me as (poorly) reported by Ars Technica (see https://arstechnica.com/information-technology/2014/03/mozil...), they were not "his employees". They worked for an entirely separate organization from the one I was running.
Back-story: Mozilla Foundation is a 501(c)(3) non-profit set up in 2003 (I was founding board member, and a co-founder of mozilla.org in 1998 at the start). Mozilla Corporation is the for-profit, wholly-owned subsidiary of the Mozilla Foundation which exists at arms length to make taxable revenue from Firefox. The two orgs are loosely connected; the Mozilla Foundation is much smaller and all about getting and giving grants.
This is actually not true. For example, it would have been illegal for Mozilla to fire Eich for his donation. This is because political activity is considered protected in California (like gender, race, etc.), so firing someone for making a political statement or for donating to a political cause is illegal.
We will probably learn more about this defense as the Google/Damore case proceeds.