If Naruto was able to read good/evil intent, I'd hope the Sage could too and wouldn't have given Sasuke his power if he sensed evil.
That said, it would certainly be interesting if the Sage didn't agree with Sasuke's answer or sensed something disagreeable in him (not quite evil....Sasuke was never evil he just did what he needed to do without regard for what was universally accepted as "good" or "evil").... but gave him his power anyway to correct his previous mistake of choosing one approach to peace over another. Maybe he just decided to have faith in both his sons and hope they'll reach some sort of compromise.