I spent more than my share of time telling groups to pick up the pace back when I was an assistant at a local club. I hated that part of my job, because you have to confront people. But I also realized it's not necessarily that you confront people (or most of them anyway) but how you confront people.
And it's also not jumping to conclusions and assuming that it's just one group causing the problem, but knowing how to do your job and knowing what to look for, because a lot of times it's not just one group, but maybe a group two groups ahead.
I always despised it when we would be playing somewhere and a course ranger would pull up from behind us, and just assume that because we were off pace, despite waiting on the group ahead of us, we were slow. "Uh, nah. You're obviously new at this, so let me explain to you how this works. You start at the 9th green, then drive backwards, to the 9th tee. Then you drive to the 8th green, then back to the 8th tee, and so on and so forth. And the reason you should do that is so you can see exactly where the slow group is, as you're going the opposite direction, so you then have a better idea that maybe it's the guy's on the 6th hole who are slow and who you should be confronting and not the guys on the 3rd hole waiting on the group ahead before they can hit their shots." And it never failed. "I know how to do my goddammed job, son. If I say you're slow - you're slow." And if I say you're an ignorant, stubborn old bastard, then you're an ignorant, stubborn old bastard.
So just in that example, which I have dealt with on several occasions during a painstakingly slow round, there were two major problems: (1) he didn't know how to do his job (probably because he didn't care) and (2) he didn't know how to confront people, and again - probably because he didn't care. He was most likely only working there for the free golf, the facility needed a warm body for the job, and called up the craggy old codger who was probably supposed to have the day off and playing.
And the other thing I see far too often - they have these young teenage kids sometimes who work for the course come out and marshall pace of play. They have no idea how to confront older people... although they should because they represent the facility - they're not getting an ounce of respect from people old enough to be their grandpas. That's just guaranteeing that this kid will hate his job, or even worse - get into a pissing match and then create an even bigger problem.
This stuff ain't rocket surgery... but some courses sure make it seem like it.