2. Has the judge set a nasty, dangerous precedent?
Precedent was already set in Nicholson v Grainger plc
This ruling merely follows the already set guidelines.
The appropriate test is to ask if a belief is genuinely held, not merely an opinion or viewpoint, a belief substantial enough to have an impact on human life and behaviour, the belief must be cogent, serious and cohesive, and finally, (the pertinent part) "worthy of respect in a democratic society and not conflict with fundamental rights of others."
One question that arises is whether on the facts, the judge ought to have found that the belief was not "worthy of respect in a democratic society."
In an assesment of the judgement I would conclude that the argument is not that the belief that there are two sexes was not worthy of respect, nor was it the belief that speech should not be compelled.
But that the action of refusing to call a 'trans' person byt their preferred pronoun was incompatible with human dignity, and this is what lead towards to the judges conclusions.
Understanding the legal position, my personal position is that it is orthognal to the act of discirmination whether the belief held is worthy of respect. The only relevant consideration ought to be whether the belief manifested itself in a way which was discriminatory itself.
One thing you might find interesting is that there is no such requirement for the belief to worthy of respect in regards to accepted religious belief. If Maya had relied upon some religious tenet of Islam for example, she'd likely have suceeded.
1. Is it wrong to express the view there's only two sexes?
Certainly it is not wrong to express any view, that is if you hold that we have a right to absolute and free expression where it does not contradict the rights of others.
The interesting component of this scenario is not the problem of censored speech, but rather the opposite compelled speech. Nonetheless the principle is the same, there is no right to compel another to act, claiming such a right is to suggest one has free dominion over another's autonomy, which is clearly unfounded.