Activist Logical Fallacy?

"If you tolerate, you are complicit."

Math wise, it goes like this:
A: Person A is morally against Position Y.
B: Person B 'tolerates' Position Y. (Tolerate in this instance meaning that Person B doesn't support Position Y but doesn't act out against it)
Y: Person A is of the position that being against injustice means you have to speak out against Position Y, otherwise you are with Position Y.
Z: Therefore, Person A says Person B is morally complicit in participation of Position Y because Person B supposedly tolerates the existence of Position Y by not acting against Position Y.

To use a real life positional context:
"If you tolerate the existence of the Melbourne Cup (a horse race), you are complicit in animal cruelty by not speaking out against the Melbourne Cup and how horses are mistreated there."

I wrote an entire blog post on this claim :) https://www.bobennett.com/posts/bobennett/stay-calm-enjoy-life.html

I don't see this as a fallacy per se, but I do see this as a rule that works sometimes, but other times is misapplied and used for manipulation. It comes down to ignoring context. For example, there are bystander laws. From a law website:

There are states that do impose a legal obligation on bystanders to intervene on a victim’s behalf. Those laws usually provide that assistance must be given to those in risk of grave harm, and so long as those helping are not at risk themselves by offering to help.

Of course, this is from a legal perspective and not a moral one, but the idea is the same. There are situations where it is clear that one would bear moral and/or legal culpability if they do nothing (i.e., "tolerate"). One example might be a person at a frat party watching one of his frat brothers rape someone.

The concept of "intervening" has morphed to "tolerating," suggesting a more passive involvement with the illegal act or typically immoral act. In my blog post I ask the question, if you are not actively doing something to stop child pornography, are you complicit? According to the interpretation and use of the rule by many, you would have to be. Activists who fight against child porn would like you to believe this because it helps their cause. The problem is demonstrated using a reductio: If there are a hundred thousand causes, it is absurd to think we are complicit in the social and moral evils of 99,999 of them if we spend our time fighting against just one of them.

In conclusion, no specific fallacy, but certainly an area where people are manipulated by activists because they either don't think about this enough or they fear the social backlash for refusing to join their cause.

This sounds similar to the argument that "You, Mr. activist, take a bus to work, so you use the very fossil fuels you disparage, hypocrite!"

Someone can correct me if I'm wrong, but I think the argument you present can therefore qualify as a tu quoque ("You, too"), though I'm not sure if that's the best answer.

Of course, one could argue that each of us "tolerates" every evil in the world that we aren't actively battling, with the possible exception of the countless evils we don't even know about. I don't speak out against China's alleged mistreatment of Hong Kong partly because I think my country's treatment of Iraq, Afghanistan and Libya are infinitely worse.

There are other things I "tolerate" simply because I'm overwhelmed by other issues. And I don't speak out about some issues because I lack information or expertise.

If Don Quijote was alive today, he'd have a heart attack before he even rode into battle.

P1) Tolerating morally reprehensible things makes you complicit.

Implicit P) X is morally reprehensible.

P2) You tolerate X.

C) You are complicit (in the continuation of morally reprehensible things).

The argument is trivially valid, because it stands to reason that, if tolerating bad things makes you party to them, that if you tolerate a given bad thing, you're party to it. The problem is the premise P1, and the implicit premise that follows.

The implicit premise is causing the argument to beg the question by assuming that X is morally reprehensible, without explaining how or reasoning through that assumption. People with strong views, like activists, often do make this mistake as they see their beliefs as self-evidently correct. The first premise (P1) is also problematic, because it ignores power dynamics and the limits of individual responsibility. Most people do not have the ability to stop bad things from happening on their own, so they are begrudgingly tolerated. That's not a true reflection of their moral views, however. Calling them 'complicit' assumes they have more authority than they actually do, and may even be a subtle  ad hominem.

That said, there are times when it can be a reasonable argument - the greater the person's ability to intervene, arguably, the more likely it is that by doing nothing they are 'complicit' in it.

I've given the category 'weak argument' because in its base form, it is not convincing. But like I said above, it has the potential to be strong.