So here is my honest theory, and feel free to ignore it:
I feel like in a lot of games violence is used, or implemented in systems, as an end in itself, rather than as a tool to use in resolving a conflict, because:
* violence is the most fun subsystem
* the reward mechanism of the game expects violence
* violence is both genre- and medium-appropriate
I feel like this can cause a play problem in AW where people perceive the enemy they want to "kill" before they perceive the reason they want to kill them -- to maintain order in the camp, to take away their followers, to acquire their resources, whatever. This question comes up repeatedly in this forum: "well, what if I just want to kill him?" It's always a little confusing to me. I regularly see players play sociopathic murderers, but usually they're not actually homicidal maniacs -- they're not killing people because their dog tells them to, it's because they have a PLAN, even if that plan is not fully clear to the character, and killing that person is a step in that plan. Just having a motivation is a plan (albeit kind of a poorly fleshed out one). So you don't just want to kill him, you want to kill him for a reason. That reason is what you seize. By force.
There's a second problem, too, which is that people love mechanics. This is fine -- I love mechanics too! But there are at least two examples in the text of players attempting an assault which could easily be "seize by force without a target" in which Vincent's reaction is...trade harm for harm (as established). Apocalypse World is a heavily MCed game, even though at first read it may not be that obvious, and not everything requires a die roll to resolve -- sometimes the MC just applies their judgement. (There is at least one example of Vincent making somebody roll in the same situation, so, judgement.)
Now, Vincent clarifies, and it's become forum wisdom, that in those (few!) situations where you really, really, don't have ANYTHING ELSE that you could conceivably want in the situation, AND you need a die roll, just use seize by force to fight people. Note that this is not really meaningfully different from just saying "when you are totally whacking on a dude and he's whacking on you and you're just hitting each other like whoa, roll +hard, choose from some options," i.e., in the majority of situations, it may as well be a separate move! Hard is the stat for killing dudes for most characters, if you want to kill a dude, and for some reason you feel like a die roll is required, roll +hard. But seize by force doesn't have to be your go-to problem-solving move for fights, just you don't actually need to make people act under fire to do anything difficult. The move you want to use in that situation is "refer to the fiction" and "ask clarifying questions." And "to do it, do it." Simplify the situation, apply MC judgement, and if you really can't resolve something into one of the existing moves, THEN use seize by force (or act under fire).
In your example I would definitely be like, well, why do you want to kill Tom? Why do you CARE that he's a psychotic bastard? Are you trying to protect something from him? That's what you're seizing by force. On a hit, that's what he has to relinquish control of or access to. If there's really nothing? Trade harm for harm. Because I don't really care about Tom, let him die. Tom's brother is just around the corner.