I can come up with handful of completely malevolent uses for facial recognition in no time flat. Automated weapons, increased surveillance, targeted marketing.
The only good use I can come up with is spotting terrorist. But they are already the one group of people who seem to have the luxury of occasionally using masks.
Involvement in this stuff could very well yield more problems with your personal conscience than what Mikhail Kalashnikov has ever had. "Someone will do it anyhow" Yes. But you can drive up the price and availability of malevolence by personally avoiding it.