Yes, it does take courage, the person doing it is likely to react poorly and it could easily escalate into a physical altercation.

for me, the worst offenders are men watching sports on public transportation or restaurants. I hate it, but I think different cultures have different norms.

It takes a bit of experience and tact. Saying "excuse me, would you mind turning down your phone a bit, please" as an opening request would not likely be confrontational especially in someplace like an airport. Few people are going to be itchy to start a fight over something like that in a place full of cameras, witnesses, security people, and with fairly limited exits.