Hmm ... let me try to explain. Fudging some die rolls to ensure that the game continues and that everyone at the table is having fun is, in my experience and opinion, a good thing!Fudging the die rolls so that the baddies always hit, make their saves, crit or generally make it feel like the DM is being vindictive is a bad thing. Does that help?
You should always have confidence in yourself as a DM, to fudge anything, for whatever reason. Just so long as you are still fair to all of the players, and trying to run the game. It's a question of whether you think the game would benefit, and just that.