What happened: returning from a XC yesterday to my new home airport, a lightly trafficked class C. Turned base behind another C172 from my flight school at the appropriate distance and normal speed on final. They land, and roll out, and just keep on rolling and rolling almost halfway down the 7000 ft runway. They're still on the runway when I cross the threshold, so I decide to go around.

I didn't know what was going on with the other plane, but I was taught not to land with another plane on the runway, and that going around is not a big deal. So it was a simple decision for me.

After telling tower I was on the go, the controller asked "say reason for go around" clearly annoyed. So I told him "airplane on the runway", and he shot back with "you guys can land on the same runway with 3 thousand foot separation". I didn't feel like having a discussion on frequency at that point, so I just left it at that. I'm not sure we even had 3k foot separation, but it's a moot point to me because it didn't feel safe.

Looking back, I can't help but think I didn't mess up here. I almost certainly could have landed just fine and exited the runway well before the guy ahead of me, but what if something went wrong? Why take the risk? If I ended up trading paint or worse with the other guy on the runway, 91.3 says it's my ass, not the controller's. I don't think there's an operational need for it either, because this is not a super busy airport (this ain't SFO).

I'm posting here to see what others think about the whole "you can land with another plane on the runway if you have enough room” thing. Have you heard of this at other airports?

Any CFIs out there comfortable with training students to make a judgment call like this on short final ("he's still on the runway but we can squeeze in behind him")?

EDIT: Wow, this really blew up. Thanks to everyone who weighed in here. My key takeaway from this is that yes, it is legal. I had never came across this rule before, in fact I was taught that the runway must be clear, period, before landing. Next time I'll ask the tower "how's the spacing" so we're on the same page about whether I can put 'er down. Then again, I'm not a fan of chatting on the radio on short final, so we'll see.