We should not confuse cultural overlap with ethnicity. We are not Arabs but we share culture with them due to proximity and religion. We are both nomadic people, people of the desert.
Somalis always wore two pieces of clothing pre-islam(two blankets) like ancient Greeks. Does that make them Greeks? Of course not. What people oppose is the claim that Somalis are arabs. It is offensive to anyone who is Somali and doesn't have an arab mother(that Somali with the arab mother can claim to be half arab rightfully).
It is very offensive to claim you are an arab when you are not and you speak as a Somali on behalf of Somalis. That is the beef.
Some ppl cant help but scream somali are arabs