Explanation of Surah 9:64?

It says something like "say mock [as you wish]." in part of it in Sahih International translation We should not assist in sinning We should command good and forbid evil So how do we tell munafiqs "mock [us/Islam/Muslims]? mocking is a sin and not a good act. How is it explained? And do not say it is abrogated JUST BECAUSE it seems to contradict other verses. This is not a convincing method if used without evidence (hadith evidence).