It is entirely reasonable for a restaurant to cater for different dietary needs, providing the policy is clear before booking/eating. Diners can make their own assessment.

I would not expect a kosher restaurant to sell shellfish, a sushi bar to serve roast beef with trimmings, a restaurant specialising in French cuisine to sell me a take away curry.

Businesses have every right to adopt (legal) policies which suit their commercial interests. I don't expect Tescos to sell car tyres, or Halfords to sell bacon butties (unless they so choose).

It is sheer arrogance for a minority dietary interest to insist on special treatment. Those businesses which wish to fulfil their needs are very welcome to do so.

I read somewhere (can't find it now) a landlord is banning cooking of meat in his property. I wondered if they can make that a condition?

That would be difficult to enforce and probably questionable legally as it might ght amount to discrimination.