Terribly unrealistic, of course. No actual interstellar empire would refuse to give aid to slavers. On the contrary, the imperial core would give them more aid in order to quell any slave uprising.
Eh, considering the period this was written, sci fi was associated with both technologically and socially advanced people, with the basic assumption that something like a communist society would allow for technological development unparalleled in history.
Imagine Taliban with their treatment of women, queer people, freedom advocates, and dissenters. Or Imagine DPRK. Now with an entire planet's worth of control.
Would you willingly give them technology so they can oppress their own people better?
When it comes to treatment of women by the taliban hazara women have it bad enough that it's been called genocidal, and it's a rather racial and religiously motivated abuse. The group is pretty large and the US engagement with Pakistan, Afghanistan and Iran hasn't exactly been good for them, so if the OP is usian it would be prudent for them to know about their plight.
Also called sanctions (we do those all the time, and it is usually only the poor suffering the most) or the morally superior prime directive.
Sanctions can be necessary, and usefull, but incredibly hard to do right and target them correctly. Sanctions also suck at changing whomever is target for whatever.
Based on a book by Dan Drezner, sanctions aren't impactful. However, the threat of sanctions is. In order for the threat to be credible you need to follow through with actual sanctions whenever they are threatened and the other party is non-compliant.