There is a difference between "condescending" - and advice that will help quite a few people from mis-identifying marbles as buyers by seeing things that aren't there - often by projecting hopes upon them. This avoids disappointment and over-paying.
I can't count how many times I've seen buyers buy a marble hoping it was a mica - to find out that its scattered oven brick. There are many, many more examples - such as damage quickly interpreted as a "pontil".
Being capable of accurately identifying marbles is the biggest help to collectors in their journey. Moving away from the growing "I hope it is rare" trend is important IMO. With fewer people going to marble shows a few times each year, the opportunity to learn with marble in-hand has become much less common that it used to be. Marble show attendance is a way to factually learn at an accelerated pace with an immense sampling set. But now that has waned and people are struggling to learn only by looking at a photo - some of which are poorly focused and over-exposed.