Yes, using weapons is unfortunate. The decision to ever use a weapon should be made with the utmost discretion. But when it comes time to use a weapon, it seems hard to argue against having the most effective weapons that also have little collateral damage.
Maybe people are worried that a new, extremely effective weapon will be discovered which happens to have high collateral damage. That's a concern, but it's never been possible to delay the advancement of technology. If something is possible to discover, then it seems like some diligent researcher will eventually discover it. But the concern itself seems misplaced: most new weapons have less collateral damage, not more.
By a huge margin, the most plausible military application of anything this company develops is "a fusion reactor on an aircraft carrier."
And I say that as someone who regards it as deeply unlikely that this company will create any major step towards a fusion reactor.
But about right for a submarine.
The problem with direct-fire weapons is not something like "bullets don't do enough damage." It's aiming and range and so forth. A plasma weapon seems unlikely to have good range or good aiming, and if it does not come with a fusion reactor alongside it, it's also kind of hard to see how you'd power the damn thing.
I'm sure someone can imagine some upside to such a weapon, but in practice, the odds that that particular result would come instead of a million other variations that would be inferior to just shooting bullets at things seems deeply unlikely.
And as everyone has already said, we already have fusion bombs. And for that matter small tactical nuclear weapons for more battlefieldy uses.