What if Liam told a story about trying to lure kids into a van so he could rape them but he didn't actually go through with it and was now ashamed that he ever wanted to rape kids? Would your first reaction be 'what a brave guy Liam is for admitting that?' I'm guessing no.
The story is not someone admitting that they used to hold prejudiced views. The story is a guy admitting to being such an extreme racist at one point that he was willing to murder a person based on the color of their skin. It's incredibly fucked up and deserves to be treated as fucked up. Why rush to immediately forgive him and play off like he was admitting to nothing serious? Forgiveness comes after condemnation, not instead of it.
And for fuck's sake, he even used the term 'black bastard' when telling the story - even if you're describing your thoughts at the time how do you think it's ok to use that language on TV if you're not a complete spastic?
There's probably a reason your first reaction to this story is to immediately defend the guy. It's the same reason you have strong anti-immigration views. It's the same reason you're a Trump supporter. It's the same reason you thought that Confederate statues aren't racist. You think you aren't prejudiced, but you end up on the same side as racists all of the time. Maybe there is something to learn from Neeson's self-reflection.