He used it as an adjective so it doesn't refer to anyone in his usage. He seems to have used 'ghetto' in the same way some might use 'gaudy'. I read through all his posts containing the word ghetto and he didn't define it once. You seem to be reading things that aren't there. So again, how is someone thinking a product (that you didn't create) is ghetto offensive?
Let me break this down for everyone. I think the problem here is both in the OPs use of "ghetto" and in the respondant's interpretation of the OPs inference in using the term.
IMO, the OP used the term "ghetto" incorrectly. Referring to something as "ghetto" is typically referring to something that is in major disrepair or is a makeshift device attempting to simulate a more expensive device. For example, ghetto headphones would be if someone stitched two left earpieces from two non-working headphones together to make a working pair. Another example would be if someone spray painted a cheaper set of headphones and added the "Beats" logo on them to make them look authentic.
Beats headphones are not a priori ghetto. In fact, a new set of beats headphones may be called ghetto fabulous, but not ghetto themselves. Whether you think Beats headphones are overpriced for their quality is one thing, but in the strictest sense, they are not in themselves ghetto headphones.
Now comes the part where someone could be offended by the OPs incorrect use of "ghetto". From the context, the OP seems to think that Beats are ghetto because they are associated with a hip hop mogul, or perhaps, a black man. This ties the use of "ghetto" to african americans since there is nothing about the headphones themselves that would be considered ghetto in the correct usage of the word. If Beats had no association with a black man, would these be considered "ghetto"? Burberry has been generally popular as a haute couture item among african americans, but is burberry items considered ghetto? I would say not.
Therefore, I think we can conclude that the OP needs more precise diction so as not to seem ignorant or mistakenly (or not) reveal an underlying racist attitude. Also, we should conclude that people shouldn't get so butt-hurt when people online write posts that may seem racist without further clarity as to their implied meaning.