There are other organizations that promote ASL and the teaching of ASL, so I don't see why the HLAA shouldn't promote other services for people with hearing loss who don't necessarily need or want to learn another language (ASL), or who want to be better able to function in the hearing world that they are used to. The term "hearing loss" implies people who once had a certain amount of hearing and now their hearing is less than what it was. Most people with hearing loss lose it as an adult, so hearing and speaking are what they know and are accustomed to doing. Most people with a hearing loss aren't completely deaf, so the services offered by the HLAA may fit their needs better than an organization that promotes learning ASL.
I honestly didn't know anything about the HLAA until I just now read their website, but it looks to me like the Hearing Loss Association of America helps people who want to use hearing aids, cochlear implants, CART services, and other methods that allow them to not have to learn another language and lets them communicate more easily in general with other people who don't know ASL.
I think it's actually a good thing that there are different organizations that offer different services to people who are deaf or have a hearing loss. It allows each organization to specialize for individuals' specific needs/wants. As for the HLAA being "audist," they are promoting services for people who had the ability to hear and who want to hear better again, so of course they're going to promote the ability to hear as a good thing. The organization was founded by someone who lost his hearing as an adult, so his organization was focused on people who have hearing loss, not necessarily people who were born deaf. There are people who have hearing loss who don't need or want some of the types of services that people who are deaf/Deaf might.