Is there a link between immigration and

terrorism?
The jury is out on that one - and likely to stay out. Even talking about the issue puts one at risk of being labelled "racist".
It is however an issue I have been thinking about a good deal of late. 
My paternal grandfather was a good man, a very good man. He was staunch Presbyterian, an "elder" of his church. He often went to church twice on Sundays. He supported church activities. He helped other parishioners in need.
Unlike many of his fellow church goers he also supported those of other faiths. The local Roman Catholic orphanage of the day knew him as the man who bought cases of fruit from growers in the hills behind the city. He would then put them at the front door of the orphanage, ring the bell and then walk rapidly back to his old FJ  Holden and leave before a nun could appear and thank him. 
He didn't actually want to be thanked. He only rang the bell to  be sure they knew it was there.
Three nuns came to his funeral - in the days when nuns didn't normally leave the convent - except in pairs. They most certainly didn't normally attend a Presbyterian funeral service.  
My grandfather's tailoring business was in the port area of the city I live in. It was where he had grown up. His mother, my paternal great-grandmother, often had homesick sailors in for a meal, a bit of mending, a chat. They came from all over the world. My paternal great-grandfather, a ship's pilot and maritime cartographer, would "bring back strays" - often men who didn't want to go and get drunk on shore leave. Of course some of them were Muslim - and other faiths too. 
I never knew my great-grandparents but I knew my paternal grandparents extremely well. They taught by example with my grandfather bringing home occasional strays - but not without first asking my grandmother to put extra potatoes on. As a child I met people from a wide variety of backgrounds. They were just people to me. Some of them "looked different" but I saw them as people. They might believe something different but I don't remember those being mentioned. My grandmother would talk to them about their families and their childhood. She had just three years of schooling before being withdrawn to work on the farm but she knew more about the world and other beliefs than most women of her day. Both my grandparents simply accepted people for what they were - even if they privately strongly disagreed.
The Senior Cat is the same - and I hope his children and grandchildren are as well. We try to accept people as people not as what they believe. I have friends of every conceivable faith and belief and I hope it stays that way. I don't necessarily believe what they believe but that doesn't stop us enjoying each other's company. 
But it is getting more difficult. I sense a growing wariness and unwillingness to communicate between my Muslim friends and other people. Some of them are tending to isolate themselves. They don't stand and chat the way they once would have done. One admitted to me that there is increasing pressure to attend Friday prayers, wear the hijab, and be outwardly much more devout. Another agreed. Things are changing.
I don't know whether there is a link between immigration and terrorism but some of them believe there is, at very least, the potential to develop one. 
If they isolate themselves then yes, it could happen. I'd rather keep my friends.