Have you never heard the phrase “the ends justify the means” before? It’s a pretty common phrase.
It means that any action, no matter how unethical or morally reprehensible, is acceptable as long as it is done to accomplish a goal that is deemed good.
This is the tankie attitude.
To reject this means that there are limitations on what actions are acceptable in pursuit of a goal. That there are some actions that are too repugnant to be justified.