Can a business make you wear their clothes with no discount and send out threatening texts if you do not wear them?
If you are employed by them, yes: an employer may set essentially any terms and conditions it wishes on employement, and such terms and conditions may include having to buy (at retail; i.e. no discount) and wear its clothing. You could be fired "for cause" for refusing to do so--that is, fired for violating workplace rules or your employer's instructions, which means that you would be ineligible for unemployment compensation.