There was one chair thrown and no "bottles". And the chair was thrown after several fans were attacked. As for the pacers fearing for their safety, there was no problem untill they attacked a innocent person in the stands.
You cannot excuse their behaviour.
Fans were throwing everything that wasn't nailed down. An official got hit with a water bottle that spun him around. People were throwing cups of ice into players face. The guy that threw the cup of ice which started the whole thing grabbed artest from behind and started to sucker punch him. Jermaine O'Neal was attacked and punched repeatedly by some big black guy with credentials on. You better take a closer look at the replays.