That's a pretty fine gray line. What sort of temptation is NOT accompanied by the thought of "what if"? And who has so little imagination that they wouldn't ponder something of the choice to do, or not to do, the tempted thing.
It's hard to call it temptation if it's not attractive enough to cause one to have to make a decision.
So I guess I'd cut someone slack for imagining the act, and only denounce them for doing the act. What of starting to do it and then stopping? That too shows weakness but then courage, maybe even requiring more than not starting in the first place. Maybe...
Tough call.
There are always exceptions to that rule. A friend of by brothers is a conservative Catholic, a newspaper columnist who constantly stands up against evil yet all his life he has had male attraction/temptation. Yet he does not submit to his temptations nor does he entertain them. His faith is far stronger than his weakness and he refuses to let that darker side rule. His submission is to Christ and the rule of the Church. I must say that I am hard pressed (pun not intended) to think of a man I admire more!
Blessings
Mel