In behavioural psychology the antonym is "punish". There are positive/negative axes (whether a stimulus is added or removed) and reinforcement/punishment axes (whether the consequence is desired).

Negative reinforcement is what boot camp uses. If you square your corners, you won't get shouted at. The "negative" aspect relates to the lack of shouting, and the reinforcement relates to the fact that the shouting is unpleasant.

At home, positive punishment would be making fun of the tendencies, and negative punishment would have meant receiving no validation for the behaviour.

I think GP meant deinforce to be a complimentary antonym, where you gave the gradable antonym.

@elliottkember is giving the correct complimentary antonym to "reinforce" in behavioral psych - "punishment" reduces the frequency of a behavior, "reinforcement" increases the frequency. There's a spectrum, but the terms only refer to the opposing effects on behavior rates. In the GP's comment, "deinforcement" appears to also mean "actively reducing the frequency of the behavior".