Re: how many back talk would you take?
I don't know what you consider 'back talk'. It sounds like a really strange expression to use when you're discussing a conversation between two adults. 'Back talk' sounds like you tell a child you're in charge of to do something and they say they won't, in a rude way... It's hard for me to see how that applies to adults.
I guess you have to figure out if they're responding to your comment as a way of furthering the discussion or as a way of stopping the discussion.
If they're responding in a way that seems like they want to discuss your idea or comment, then, well, it depends if YOU want to keep discussing it or if you think their point might be interesting or if you think you want to try to convince them of your original point. It's kind of up to you if you want to continue discussing with them or not.
If they're responding in a way that seems like they want you to stop making comments on their technique... then stop making comments on their technique. In that case, they don't want you to teach them, so just train.