As a Muslim relative of mine said "there is no progressive Islam".
And why do people like the father in the op move to the UK, where they obviously disagree with the culture, kaws , lifestyles...? Anywhere he lives would be a steaming cesspit to him. But here he would get state benefits, housing, free medical care and education for the kids, no secret police monitoring his activities (with the risk of him and/or his family disappearing one fine day), no laws to stop him spouting crap and - here's the best bit - he can stand on the street, spouting bile and hate against the country, its people and its laws and get police protection whilst he does it.
What do you think the Saudi secret police would do with the likes of Chowdhry? Give him a cream tea and a medal, or 'vanish' him off the face of the earth?