The difference is, Geekke had plenty of time to work with the team the past summer and all canp/preseason. If Tampa was locked in to a playoff spot and the division wasn't on the line, sure, play Howard a few minutes in a few games. Having an inexperienced and unproven rookie come in cold in the most important regular season games of the year and expect them not to make critical mistakes (due to lack of NHL experience and little practice time) is unrealistic.
If Howard wants to play that game, that's also his right. However, in that case, JBB would be better off exploring a trade for him this summer. No one player, especially not a rookie who hasn't played a game yet, should try and hold JBB and the team hostage like that. If JBB and the team feels it's the best course, they will, but that has rarely been the case with Tampa.