Dealing With Conflict
We all run into conflict, as much as we may try to avoid it. But the way you handle that conflict can be an instrumental tool in how you define your gym's environment. It is easy to get defensive, especially when someone is critiquing something you are so prideful in.
But, if a client is bringing up a negative emotion they are feeling towards your training process - validate it. If one person is strong enough to bring it to your attention, chances are a couple other people are feeling similarly.
Rather than dismiss and deny the feelings someone is sharing with you, take it as a learning experience on how to grow. The same with training - you only get better from correcting mistakes and improving.