I would approach this by bringing up (one on one) concrete examples of where this person displayed a lack of tact (without calling it as such). If the other par

I would approach this by bringing up (one on one) concrete examples of where this person displayed a lack of tact (without calling it as such). If the other party reacted strongly, analyze that and get this person to understand cause-and-effect, along with explaining that there are other ways of accomplishing their goals. Come with concrete ways of how you would have done it. If the other party reacted privately to you, instead talk about how you would feel, perhaps even ask them to imagine how they would feel if someone talked to them in a similar way. Don't make it personal at any point, your goal is to help them see that there are better ways of accomplishing their own goals. I find most folks are open to that kind of feedback. If the person is an incorrigible asshole, you may need to escalate.