I don't take or give gimmes. The stroke is just as important as the 150 yard approach to the green. Besides I like sinking a 2 foot par putt. That's what the game is all about.
I've had random playing partners putt a ball back to me and say it's good before. Unless it's sitting on the lip I'll just politely replace it and finish the hole with a smile and do it politely. That snuffs the problem and they understand that I putt it out, and they don't bother with "that's good" any more as if they're the USGA director. Of course there are a lot of ways to do this, nicely or like a douche. I say something like "Gotta get my practice in" and smile when finishing. If one were to do this with a deadpan expression and remain silent it would be very awkward. Lol.
Who wants to hit the ball towards the hole but never put the ball into the hole? Is there no satisfaction in burying the ball and grabbing it out of the hole???