It's certainly possible some people don't talk to you because of your heritage. In fact, they're doing you a favor even if it doesn't seem like it. Why would you want to talk to people who judge people solely by their ethnic background or religion? Be thankful they've removed themselves from the pool of potential contacts, so you don't have to waste time finding out that they're...simple-minded is a nice way to put it.

In my experience, some people really do not want a language partner who isn't, say, a French guy who can trace his family tree several generations back in France, with what they consider to be a classic French appearance, typical French name (or what they imagine it to be), regardless of whether the person can even spell or construct a decent sentence in his language...

That said, who am I to judge? If that's what they want, that's what they want. Their loss, if their criteria are so laughable. I feel bad for them because they're unlikely to learn anything with such shallow parameters.

I've also met people who don't care at all where you are from or about different facets of your identity. They just care about what you know and who you are. So, forget the simple-minded types who aren't going to do very well anyway. There are smarter people around.