Arguably it is those that have the most objectionable views that SHOULD be those that are at the centre of the test cases.
Human rights are for everyone. Even those we don't like. Even those we find objectionable. Enforcing them for those we find objectionable means we are more likely to enforce them for everyone.
Even if someone IS homophobic, or racist, or <insert blank>, they should not be discriminated against on the grounds of their sex or their lawfully held beliefs. For example, I can think of some people that I know with strong religious views that I find problematic because of the way their beliefs influence their views of (in particular) women and homosexual people. I abhor their views of women and homosexuals, but that doesn't mean that they should be denied the services of their union because of their beliefs - which is what SP is alleging has happened.
(FWIW I am not surprised about this judgment - I thought it was inevitable once it became apparent that RCN have a policy not to support someone who has already instructed an external legal professional.)