So what happened to page one of this thread? Very interested in it because I used to run this area all the time and had this kind of thing happen a lot.
I won't list my PRs, but I was a competitive D1 runner and when I lived in DC, was training pretty hard and running decent marathons.
One of the things that would happen to me a lot was getting passed on the Key Bridge, and then having to deal with the awkward re-pass once we hit the paved trails in NOVA or the C&O in DC. The Key Bridge is a bit of a "stage," if you will. Heavy traffic and lots of people watching since the traffic is always stopped. Also, there can be a lot of tail on the bridge. Sometimes this makes people who are less inclined to running possibly pick up the pace while they're on the bridge.
I am a nice guy, and I think that passive-aggressiveness shows a lack of character, so I will usually just confront the situation in a friendly manner. If I were the guy latched on 5 meters back, I probably would have just asked if it was okay if I ran with the guys. It is important to note that the I wouldn't really do that, I would just run on my own, but if it were really an issue where they were running the exact same pace and there was only one way to go, I'd probably say something like, "I am not trying to chase you, I am just running a similar pace."
If I were the guys being followed, I would definitely turn around and say hey to the guy. If he was nice, I might ask him to run with us. If he were creepy, I'd just tell him to go by and have a nice run.
To the "Consider This..." guy who followed another man into the woods. Now that I know you are in the DC area and not in my new town, I will share this story... I was running with a friend the other day around 6:30 am and had to take a dump. So he needed to drop his short at his car and we had just done a 4 mile loop and were about to do another. Popular running loop in town. We split and I went on to find a spot off the trail and he went to his car. I was going to take a dump and run back towards his car to meet him again.
As I am heading back into the trail, another runner - older guy about 60 or so - heads into the trail at the same time as me. So I have to go pretty bad and I have a spot in mind that is about 400 meters into the trail, so my first reaction is to sprint ahead so that I can run into the single track and go about 50 meters into the woods and dump. Thing is, the old guy starts sprinting too. I don't really mind, but when he follows me onto the singe track, I stepped aside to let him go by. NO ONE RUNS ON THE SINGLE TRACKS, by the way. They are for bird watchers or something. Very windy and short. No conducive to running or mountain biking, so when he turned off with me, I knew it was going to be weird. He kind of stops and looks at me. I just said, "man, I am trying to take a dump so I can go meet my friend for our second loop." He didn't say anything, but he turned around and ran back to the main trail.
Very similar to your situation, which is crazy... I guess these things happen.