I'm looking at it, and I see several key factors in play:
-Untyped and stacking bonuses/penalties. These are never a good idea in a game where control of bonus quantities are paramount in a game, and encourage abuse(a group of four level 1 characters TWF-ing this and a weapon would get a net +1 to attack and +3 to damage each, it only scales up with more people, particularly focusing on a target). In this circumstance the types are quite obvious, Morale should be the type, and if they are to be significant, then let them scale with the number of ranks rather than stack indefinitely. The setting concerns aren't an issue, maybe you have entire villages having a brofist based monster defense strategy, maybe you don't, but the potential for abuse remains. A smaller concern is both the synergy with bard and the diminishing of the benefits of inspire courage, as you can replicate a high level bard's performance with multiple cheerleaders.
-Action type, as an attack action, it becomes significantly more abusable, slap a Haste down and your squad of cheerleaders is now outputting twice as much cheering power and easily making the bard look bad. It's also counter to theme, your TWF-ing full BAB types get more benefit out of this than the typical skill specialist 3/4 BAB types. It's not really a weapon either, which further causes complications with other rule interactions(for example, you make a martial strike using this as the melee attack channel, the strike will attempt to modify nonexistent qualities such as accuracy or crit range. This is specifically a save-based attack and should not be classified as an AC based attack). If you want to make it usable with weapon attacks, make it a swift action(and boost the output to match) rather than this mess.
-Untyped irresistable damage, the trappings of this indicates it should be entirely mental in nature. Base resistances off mind thrust or other pure mental damage sources. Save for half isn't really a problem since it does pitiful damage that way.