Running Down The Clock

I like to play with a 30 minute clock.  Every now and then I notice that my opponent suddenly stops moving.  Ten minutes later, still no move.  A few games ago, I asked my opponent if he was running down the clock to avoid a checkmate. We were in the end game and I had 4 points on him.  His rating was in the low 900's while mine was about 950, at the time.   He told me that he hated playing people like me because I had no strategy.  That all I wanted to do was promote a pawn.  Well, why not?  It is within the rules, and in and of itself is a strategy.  Or am I mistaken?  I have also played opponents with a rating far higher than mine, and it seems that some of them when faced with a sure loss, will just stop moving, so for about 15 minutes I have to wait around until the clock runs out, or they disconnect from the game.  I believe this is poor sportsmanship.  Am I wrong?

If you don't want people running down the clock, play a 15 or 10 min rapid game.  They will be forced to make a move or they will lose the game.

I do in fact report stalling, and I block the opponent after the game.   Yes, they can use their time as they want, but you are correct, it is very annoying.  I would like to point out that I have no beef with a slow but deliberate opponent.  And it's easy to tell the difference.

Thanks for the advice.  JenniferAlex is now blocked.  Responding to LeoLou, I've tried the rapid games, but I really am not a big fan.  HOwever, I take your point.

Rar! You have no strategy! I can't stop your pawn and am lost! How dare you play chess! /s

I can't go too far as I have certainly accused users of worse for less. (Not to their face, though.)
@athenasowl938 You're fine, you did nothing wrong, report and move on. 

I agree, it is my opponent's game as well.  Unfortunately, it appears that concepts like sportsmanship are lacking in some players.  I have always finished any game I started, meaning resignation if necessary.  The one time I disconnected was when the internet went down on my desktop.  And when it came back up, I sent a message to my opponent apologizing for the abrupt departure. 

I played a twenty minute game, after 6 minutes the opponent went dead.... Their clock got down to 3 mins then they played a bunch of perfect moves and trashed me. Anyways, weeks later I noticed I was awarded points on that one, guess cheating was proven. Waste of time 🙄

Snitches?  Why?