Reasonable accommodations can be made, but if availability during those times is a core job duty (known beforehand), then the firing is eminently justified.

If your religion says you can't handle pork and you take a job at a pig slaughterhouse, the employer should not be obliged to pay you to do nothing.

This is true, but as you just said: it has to be a core job duty made clear before hiring. I highly doubt that Yelp would tell candidates "you cannot have a single day without checking your email." There may be some implicit "this is a startup, so work hard" mentality, but that won't hold up in a court of law.

> There may be some implicit "this is a startup, so work hard" mentality

Yelp isn't really a startup by any reasonable standard.

I dont think 24/7/365 however is a reasonable thing to demand

Sure, but you can't sue over that unless that wasn't demanded of people with other beliefs, which doesn't appear to be the case.

You wouldn't sue and claim to have been discriminated against; the lawsuit would claim that your religious obligations could have been reasonably accommodated by the company but were not.

Sure you can: it's not a defense to say "but we discriminate against everyone"

It is. "Discriminate against everyone" is oxymoronic.

Religion, like sex, is a protected class.

By your argument you could tell a pregnant woman “sorry, you have to work, all the men have to keep working.”

Regardless of what you personally believe that’s likely a losing case in a lawsuit.

Not sure about your jurisdiction, but political affiliation is also a protected class.

Together with religion there isn't possible to have rule or requirement which isn't against someone political or religious view. Anti-discimination laws must therefor limit themselves, often down specific scenarios or looking at the reason why a requirement exist rather than the requirement itself.

For example, if I hold the political view that working more than four days a week is inhumane, that carries just as much as protected class status than if I believed Sundays are declared by god as the day of worship and rest. If a company fired someone for not showing up on the fifth day, they have just as much right to do so as fire someone for not showing up on Sunday if that is what the employment contract says. Local employment laws naturally applies.

> For example, if I hold the political view that working more than four days a week is inhumane, that carries just as much as protected class status than if I believed Sundays are declared by god as the day of worship and rest.

It's true that in some jurisdictions (including CA), political affiliation/activity is a protected class, meaning employers cannot discriminate against or refuse to hire people because of these affiliations/activities.

But that doesn't necessarily extend to political beliefs. Otherwise, employees could just say that any of their beliefs (I should have a 2-hr lunch; employers should provide free breakfast/lunch/dinner) are political in nature and then get whatever they want. Unlike religion, which may not be the basis for discrimination and must be reasonably accommodated, I'm not sure that any of the political stuff has to be accommodated. I think employers just can't discriminate on this basis.

I could be wrong here, and am happy to be educated. But I'm a former lawyer and have followed this type of things somewhat during the last decade.

That's nice, but business necessity is, by law, an affirmative defense to discrimination claims, including those based on disparate impact. Whether the defense succeeds or fails depends on the facts of the case and a court's interpretation thereof.

It's literally part of the Griggs v. Duke Power Co decision from which the disparate impact standard arose. The 1991 Civil Rights Act puts on defendants the burden of proving "that the challenged practice is job related for the position in question and consistent with business necessity".