Well I think you need to give people credit for at least asking the question. To suggest that they should have learned everything they need to know about lift truck operation during their training and should therefore be scolded if they question something later seems a bit harsh (and counterproductive). Sometimes people need to understand why.
For example, decades ago when seatbelts started appearing on lift trucks, I (an operator at the time) didn't understand the purpose. And like just about every other operator at the time, I didn't use them. Even today when seatbelts are required by OSHA and other organizations, I still see that most operators don't use them (use is not enforced at their companies). However, when they ask why and are informed of what happens when a lift truck tips an the operator tries to jump and instead gets crushed by the safety cage, they get it. And subsequently seatbelt use is enforced.

I think you have to give the original poster a little credit for first asking the question about using an order picker with pushback rack rather then just doing it. Now the guy trying to sell him a truck that said it is OK is the one that needs a strong scolding or worse.