I think it depends on who it is. If the person is unlearned, but means well, than a helping hand is quite fine.
However, there is this 19 year old kid at my gym who deserves every lost pound he receives. On literally my first day back from a car accident, and approximately 14 weeks and 30lbs off from lifting, he and his 'posse' were using every single weight on a rack for DB Shrugs. I approached and asked, "Hey man, can I see that 45 for a second?" to which he replied, "Whatever, when I'm done with it" then proceeded to stop the weight he was using, pick up the 45, and use it. So this cat finishes his set, puts the weight down, looks up at me from his seat and says, "There you go, don't hurt yourself".
The only expression funnier than my surprise at him saying that was his surprise when I fed him a shot in the teeth when he was done his workout.
I seem him now with the same inflate and deflate cycle as the rest have mentioned.