People like your mother in-law are noticing changes to the country they don't want and never asked for.
1) People are only now beginning to realise multiculturalism doesn't work and never will. Just look abroad, Sweden is a **** show, Holland regret their openness to other demographics.
2) Too many mosques are getting built in towns. This is a traditional Christian country.
3) There are many coming here that don't live by the line: When in Rome, do as the Romans do. Many foreigners don't respect their new culture here or even try to embrace it. Some have been here 5 minutes and think they own the place.
I'm with your mother in-law on this. I don't want them here and certainly don't want to be overrun with them either. Also, many are a liability, non skilled, criminals back where they came from. We see loads begging on the street and even sleeping rough (they're hardly having a better life being here). We need to sort out our own problems, take care of our own, before bringing other demographics into the UK.
Also, it's not racist, it's using your head and common sense as it's just going to get out of hand, in fact it already is. A hammer needs to be put on it ASAP.