"Punish him economically," Gelles says. "Tell him to pull over, then pay the fare. … But don't tip."
Keating agrees that the situation is tough.
"You're in the back of a cab, and to some degree, you've given over power to the man in the front seat."
But Keating also encourages people to step up in this situation.
"How would you feel if you let this guy go on? By not challenging him, it reinforces his views," she says.
At a restaurant, a stranger shouts into his cell phone and you can hear every word of the conversation. Do you change tables? Ask him to be quiet?
Gelles describes this as more of an etiquette violation and recommends ignoring the offender or leaving.
However, if it's really bothering you, he says it's OK to "ask him to tone it down."
You're dining with your significant other and out of the corner of your eye you notice a couple at the next table getting what you consider to be overly affectionate.
Do you change tables? Complain to the manager? Tell the couple to knock it off? Or do you relax and enjoy the show?
"You have to ignore it," says Gelles, who again recommended that people could influence these situations through economics.
"You change where you're sitting, but it's the manager's problem. The only way to get the manager's attention is economically. Say, 'I'm leaving. If you want to run a brothel, that's your business.'"
Keating says sometimes it's OK to intervene in this type of overt public display of affection, aka PDA.
"If the PDA was outside of what would normally be expected in a restaurant, and if it was affecting the enjoyment someone was having or was really distracting, certainly asking the couple to calm down would be appropriate."
But what if the man gets a call from his wife and he insists he's at the office even though he's clearly not?
"Be very slow to judge other people," Keating says. "There's always a story."
In general, how we perceive ourselves influences whether or not we step up and step in, Keating says.
We decide to intervene because we are confident that we have the tools to make a difference; sometimes we identify with a person who needs help, and sometimes it's because we view a situation as a violation of social norms and wish to right it.
The overall message, Keating says, is that people must do their own calculations when it comes to deciding whether or not to intervene when confronted with an ethical dilemma.