A relationship with the developer of or company controlling a piece of
proprietary software is like any other abusive relationship. Often, the
relationship is perpetuated by emotional or practical dependence on
perpetrator, sometimes to the point that the victim will defend their abuser.
When someone you care about is in this kind of relationship it can be very
frustrating. However, you can't force them to change their mind, and if you
push too hard you will lose their trust.
I think the solution is to intermittently communicate the problems you see
over an extended period of time, and hope that they'll begin to see it on
their own. When I talk to someone about the importance of privacy and
software freedom, the conversation always ends with them unconvinced. Often
though, if we talk about it a few weeks later they'll have started to reach
some of the same conclusions after making their own observations with what I
said in mind.
It's a slow process, and only a solution at the individual level. However, if
society as a whole is doomed then the best we can do is mitigate the damage
to ourselves and the people we care about, and if society is not doomed then
we should keep doing our best.
I was watching an interview with RMS a while ago and he was asked if he
believed that the Free Software Movement will win. He responded (I'm
paraphrasing) that if you believe you will win you risk underestimating your
enemy, and if you believe you will lose you risk giving up when you could
have won. Either way, there is no benefit in trying to answer that question.