I think you’re misunderstanding it. He absolutely initially meant “go into the arts” as a career, that would likely result in a lifetime of poverty. It’s part of a joke about disappointing your parents, which is a personal issue for him and a reoccurring theme in his writing. He then transitions into offering advice about the personal value of making art for the sake of it.

He was a transgressive, sarcastic writer. He isn’t speaking poorly of homosexuality, or artists, merely referencing each group’s lack of status in society at that time. His message is to be true to yourself, do things that make you happy, even if they result in social ostracization.