Accident at walmart with knife employer responsible?

Talk to your union rep, that's why you have one.

You cut your self, not the employer. They provide you with the equipment, they expect you to know how to use it properly. It's your responsibility to follow proper safety procedures, so you don't get cut.
As for firing you, they can fire you for any reason. If you keep harassing them they can fire you for negligence.

Employers are NEVER responsible for an employee's negligence.  YOU cut yourself with the knife that YOU were using.  How is that the fault of your employer?  Sure they can fire you.  Careless, reckless, negligent employees - not the best type of employees to have working for you.  But it doesn't mean that they will fire you.  However, if you keep harassing them and blaming them for your negligence, they probably will.

Sounds like you need a union

That is Wal Marts way, screw the employee. And for the guy that advised talking to the union rep; Wal Mart does not aloud a union in the store change. Places that have tried they just closed the stores: PERIOD!

As long as it is a safety knife that they supplied you with and you were shown how to use it, seems like they have no reason to fire you.

If you are fired, it's not because you cut yourself. It's because you violated a company policy. Was the knife supplied by and approved by WalMart? Were you using the knife in a manner and for a purpose that is consistent with your training?