Yeah, the paragon/renegade stuff could get a little odd at times. Nevertheless I like to think that you're not really supposed to pick all paragon or all renegade since nobody thinks and reacts in a completely consistent manor. For example, one of my colonist Sheps has an irrational hatred of Batarians and she tends to react more aggressively when they're around. With my main Shep I tend to play from the gut and just so happened to end up with a roughly 80/20 paragon/renegade split.
It's interesting to me how a lot of players can't help but perceive renegade as "bad" when it's supposed to just be a different flavour of "good." Renegade just means taking the Dirty Harry approach as opposed to the Paragon "boyscout" approach. For example I watched part of an ME2 'let's play' on youtube a while back and I noticed that when this guy (who was an old school D&D type who went on and on about the roleplaying side) got to Legion's mission and made that decision, he baulked because he wanted his Shep to take the renegade option but instead chose paragon because he didn't want the renegade points.
I suppose it's really Bioware's fault by choosing to colour code them red and blue since they're almost hard-wired into western psychology as meaning "danger" and "peaceful", respectively.