Well they shouldn't expect good training from someone they don't think is a good employee. No offense, OP.

Clearly you weren't very good at your job

Well what did they expect

If you were an artificial intelligence, we could all breath a sigh of relief that the singularity didn't happen.

Sorry, OP. If they really thought you were that bad at your job, they should've worked with you and given you additional training, rather than having you train someone else. What are they gonna do, fire this person but have them train someone else first and let the cycle continue? Hopefully you get another job soon and do better at that one.

If you have a sub par employee and you give him a trainee do you really expect the trainee to be an improvement? YDI to your former boss

You boss sounds like an incompetent jerk. Send him a bill for your time, as you were no longer on the payroll when he called and he was taking up YOUR time. He deserves the extra annoyance that would cause him when he receives your invoice in the mail.

Damn, that's messed up. The boss firing you was one thing. Calling you to verbally abuse you was a whole other thing that definitely crossed the line. Even if you were bad at your job, you did not deserve to be treated like this. I'm sorry, OP.

This is just one of those that makes you feel bad for humanity as there are some really mean people here.

Did you know that your boss thought you were performing poorly? I'm sorry you lost the job and then got verbally abused. I hope you took the opportunity to tell your former boss off.