Although it hasn't happened in the comics, Jaime Reyes did turn *temporarily* evil in the cartoons Young Justice and Batman: Brave and the Bold due to the Reach controlling his scarab. So, as a regular citizen of Earth, if you saw the Blue Beetle as a hero who betrayed humanity by leading an alien invasion, then turned back into a hero (explaining it was the scarab controlling him), would you be able to trust him again?

I think it'd be a pretty cool story arc for Jaime to try and win back the support of the human race (or even his friends) after his questionable actions.