They have literally told you they feel as if they do not "belong" in their specific profession because they do not see other minorities in that specific profession. They have told you a lack of, essentially, non-whites has them feeling as if they do not "belong" in the profession. That is what they have told you specifically?
I have certainly encountered the sentiment from minorities that they wished other minorities were in their profession for the purpose of having some common denominator when it came to life experiences. A commonality in life experiences to discuss with others, a commonality of values, upbringing, beliefs, etcetera, they can share and discuss with other minorities, that whites and Caucasians relate less to or cannot relate to at all. I have heard them express a sense of not "belonging" on that basis, but I have yet to encounter someone say they do not belong in a specific profession because of a lack of encountering minorities in the same profession.
Most of the ones already in the field have come to terms with feeling that they "belong", so most of them more question why they are the only one, what's going on that they're the only one (or two or ten). It's the people who have an interest in the field and investigate or are new to the field who question their "belonging". And many of them become discouraged and never start or transition to a different field. I've seen it happen.
We recently had about 3 huge socials, 3 weeks apart, that our top officer put together so we could mingle with everyone under our departmental umbrella and network and get to know each other better. About 130 people... One black guy, one black woman (who is an admin, not actually a "tech" person). The black guy, who I'm friends with, was making jokes about it - he always does. But he's right, and we all told him, "yeah, it's weird man, how are you still the only one? What the....?" I mean, what else can you say when it stares you in the face like that? It IS weird. Black people are what, over 10% of the population, but we have less than 1% in our group? Weird. Institutional racism.
And then my manager, the only female officer in our 130 person group. Other females are about 30, most of them are contract workers, not employees, and no other officer is female. Women make up roughly HALF the population and we have less than 1% represented?
Those numbers are crazy. It is undoubtedly institutional racism and sexism that's to blame. My manager has confided in me the things that she's seen and how it's perpetuated. That's why we have symposiums and events to encourage blacks and women primarily to become involved in tech.
It's not like "Oh, the Department is only 10% black" or "only 40% female" - no, it's like less than 1% black and less than 20% female with less than 1% female officers.
My company is a huge, conservative, Wall St. investment bank and they do this, even they recognize the imbalance.