does equipment get flipped with the stunned character?

for example if i have a personal force field (which can make him untargettable by plot twists) on mr. sinister and he becomes stunned, can my opponent finishing move him?

Equipment provides a character with additional game text. All game text for a given character becomes inactive when the character is stunned and remains so until the character is recovered.

In effect, equipment gets stunned right along with your character thus negating any benefits provided by that equipment.

I don't see anything in a faq or rules that states equipment provides a character with additional game text.

Is this a ruling that ude made?

Yes. In short, equipment turns off whenever the character its attached to becomes stunned. Its kinda like Scarlet Witch doesn't get her ability while she's stunned, either.