Yes, it is racial stereotyping to state that such garb is more prevalent among a certain race. However that doesn't make it racist, or inherently incorrect for that matter.The problem with this is that saying what one race wears, is, in fact, racial stereotyping.
Even if it is an established or documented fact.
Now, if Ron was to say that only black dudes wear Timberlands and, therefore, they are inferior because of it...THAT would be racist. But that's not at all what he's saying. Racism and stereotyping are two different things.