The thing is, if I was somewhat interested in a Mozilla VPN service, this spectacularly idiotic decision to deploy full-page intrusive advertising into Firefox makes it 100% certain I will never buy the Mozilla VPN service--because, how can I trust that they won't do the equivalent to that service? What's to stop them from blocking certain sites (on the other side of the VPN) as part of some promotion? Or worse?

They've made it clear they don't believe their own language about privacy and user choice. They've compromised one product to advertise another. And perhaps worse, they doubled-down about it in Bugzilla with corporate doublespeak, which to me is the tell that they'll absolutely do it again.

It's amazing how apt the trust-thermocline analogy is.