The ejection was added more recently to further discourage unsportsmanlike acts.
From the kentucky.com
In short, the play would now result in an unsportsmanlike conduct minor penalty.
From the thestate.com
The unsportsmanlike conduct penalty gave Lindell a shorter kick, and he made it.
From the washingtonpost.com
That drew an unsportsmanlike conduct penalty, which took the score off the board.
From the timesunion.com
The Tigers made it but were flagged for unsportsmanlike conduct in celebrating.
From the denverpost.com
Record numbers of players were ejected for fighting or unsportsmanlike conduct.
From the newsobserver.com
Mara is sent off for roughing while Letang is called for unsportsmanlike conduct.
From the post-gazette.com
Six personal fouls were called, along with a penalty for unsportsmanlike conduct.
From the charlotteobserver.com
Fans complained even louder when Cullen was whistled for unsportsmanlike conduct.
From the stltoday.com
More examples
Cheating(a): violating accepted standards or rules; "a dirty fighter"; "used foul means to gain power"; "a nasty unsporting serve"; "fined for unsportsmanlike behavior"