Hahaha, this is a made up word. It doesn't yet exist in English. However, since it is a play on other types of ache, the meaning is easy to understand.
Words that exist are "headache", "back ache", "stomach ache", so "smartache" means that the writer's intelligence (being smart) hurts (aches). Probably they are trying to say they only speak to stupid people, and it hurts their brain to think like a stupid person.