I'd say that there's a 25% chance of him being the original BTC_Bear.
I dont think a 75% chance is appropriate for a negative rating.
Well, that's obviously a matter of judgement or opinion.
I personally consider someone I'm only 25% certain being the person in e.g. the passport he's showing,
not trustworthy.
Not trustworthy for me is reason enough for a negative trust rating.