The Tunisian defender responded to a push by Lee Erwin by aiming a kick and punch at the striker. He then tussled with Motherwell's unused substitute Fraser Kerr.
The brawl took place towards the end of the second leg of the Scottish Premiership playoff final at Fir Park.
Motherwell won game 3-0 to wrap up a 6-1 aggregate victory over the Gers and retain their top-flight status.
Former Rangers midfielder Ferguson was following the match, and he was appalled with the action of Mohsni.
“To react like that, there are no excuses,” the 47-year-old told BBC Radio Scotland. “Mohsni is an embarrassment. I don't know why Stuart McCall put him on as he has been a liability this season.”
Former Rangers defender Dave McPherson was also appalled at the way Mohsni conducted himself against Motherwell and told BBC Radio 5 live Sport: “It has been a terrible season and to finish the way it did is completely unacceptable.”
Mohsni joined Rangers on a two-year contract in the summer of 2013, as reported by BBC Sport.
The 27-year-old became the Glasgow giants’ eighth summer signing at the time and arrived as a free agent after leaving Southend United.