I think maybe people's idea of what you need to do to be evil is out of step with what it means to be evil. Being evil isn't a record of your deeds, it's your worldview, if you've never hurt a fly before in your life, but you think Might Makes Right, then you're evil. Just because Astarion or Shadowheart haven't twirled their moustaches while murdering children doesn't mean they haven't espoused evil ideology.
Being evil isn't a crime in FR, and having an evil worldview isn't incompatible with existing in a good or neutral society. In a highly pluralistic and polytheistic setting you have to expect that there's a live and let live dynamic that allows people of wildly different beliefs coexist, Baldur's Gate itself has a pretty prominent temple to an evil deity. We might mostly run into the wild eyed cultists, but there must be a slew of stevedores and clerks who go home after a long day at work, and say a little prayer at the altar of Bane before supper.
