Well why are they booing me?

I've been wondering the same thing. This wasn't a huge deal, so I let it go. :p

I have noticed within the past few years, non played Sims will go out of their way to boo/heckle my Sims. There doesn't appear to be any reason for this. None of my Sims have evil or any other bad traits. They have not done anything foul in public either. Maybe this behavior came in through one of the last updates?

Did your sim EVER join the Music career?

Just for the record, Sims have been autonomously booing and cheering each other long before the Showtime expansion pack was released. Showtime introduced controlled 'heckling', meaning you could now choose to have your active Sim perform this action (and others).

In the past (before Late Night or Showtime) it was only Sims who were public figures which the cheering or booing would happen to, such as those who were employed in the Music, Sports or Political careers. As I stated earlier, there is a celebrity system in the base game via the charisma refining challenges. Although this celebrity system isn't as refined or fleshed out as the one which came with Late Night, it does create public response. Keeping your Sim's relationship healthy with the public is one way to put a stop to the booing.

For some reason, when creating and developing this game, the Sims Team chose to put emphasis on 'creating drama' and nothing stirs up more drama than some negative controversy of some kind; although the player won't know what that drama is, the Sims will and may respond to it.

"ItsMeThatGuy;d-999211" wrote:
Something i noticed is that people have been shouting at me and booing and taunting my Sim, with speech bubbles showing my Sim and a cross over it. One thing is that I joined the Musical career and only a lvl 2 at it. Is it because of a bug or the music career?

Since you mentioned you don't have Showtime installed then it's just one of the annoying reaction idles the game has. Luckily those don't have an affect on the sims mood just try to ignore it.