I haven’t seen the movie in decades, but I thought at that point in the movie 2 bombs had already detonated, and one more would definitely sink the ship.
I don’t recall that being the case, but even if it was, that’s no excuse for Harris’s actions. If his bomb blows up and the ship starts sinking, there’s still a chance to put everyone in lifeboats and rescue as many as possible. If all the other techs repeat his mistake, it’s going to be mass carnage and a lot of unnecessary deaths.
They’ve got a means to minimize the damage from any one person’s mistake, but it only works if he announces what he’s going to do before he does it. Harris abandons that rule for no reason, and when it’s most important. He should have been court martialed.