From what I can tell, souness is overtly non racist. When he signed Mark Walters for rangers, he warned him it might be difficult for him because of the racist crowd. Or this story from Howard Gayle on Tommy Smith being a racist cnut in the 70s:
I received the ball, controlled it, and lashed a shot towards goal. Tommy Smith was on the other team and it hit him on the leg. It clearly stung and some of the other players started laughing. I had a smile on my face as well. I saw it as karma. Tommy responded with a tirade of abuse. It was ‘black this, black that’.
The place went quiet. Everybody could hear it, including the staff. He was a legend. I was a nothing. Nobody said a word.
I’d had enough of him: this bitter old man. So I went over and squared up: nose to nose. I looked at him dead in the eye. “You know what, Tommy; one night you’ll be taking a piss at home and I’ll be there waiting for you with a baseball bat,” I said, calmly. “And then we’ll see what you’ve got to say.” I wanted to start a fight with him. And then he walked away.
I look back now and remember this moment as a real low point. I’d grown up loving Tommy Smith. He was a hero of Bill Shankly’s team. But you only see the player, the legend: the hero. You don’t know the person. From then on, he was no hero of mine. As a human being, Tommy Smith was a disappointment, a complete let-down.
Graeme Souness was the only one that came over in the immediate aftermath. “Well done, Howard,” he said. “Tommy deserved that”. Graeme was a true leader.
I don't think it ever occurred to most people from that generation who were taking a stand of some sort against racism (I mean, he's hardly being a civil rights advocate here, just a few good examples of acting against his racist surroundings) that colored people would still be discriminated in the absence of overt racism. It's probably absurd for souness this is happening, whom I can imagine in his own self view has stood up against racism at a time where doing so was probably less popular than just being straight up racist.
The issues of race today are in many ways quite different than they were back then, but the way it is critiqued is often as if it is of similar character to when overt racism was normalised. It needs a different vocabulary partly because it trivialises the debate on stereotyping when it all gets lumped into the same basket, and that in turn risks trivialising speaking up against the rising current of overt racism we do see emerging as well.