For the sake of productive discussion, let's narrow 'modern societies' to the United States since 1964 (when Title VII of the Civil Rights Act was passed). In 1965, the Supreme court held (in United States v. Seeger) that:

'The test of religious belief [...] is whether it is a sincere and meaningful belief occupying in the life of its possessor a place parallel to that filled by the God of those admittedly qualified for the exemption.'

So a non-religious person like yourself can have their 'ideology' legally protected from discrimination, as long as it passes the same 'sincere and meaningful' test that other protected religious beliefs do.

So the key to answering your good-faith question is in the definition/scope of 'religious' belief. A 'religious' belief (in this narrow context of US Title VII law) must meet a higher standard than a more general 'ideological' belief in that it must be both sincere and meaningful, and I would argue that a sincere belief meeting this higher standard is, by definition, not 'something that a person can readily change'.