Correction, I just had a listen to him on YouTube.
I don’t think he has a speech impediment, apologies, but his speech is quite mumbled and low, with very little expression. This makes it hard for the listener to tune in I think. He isn’t the easiest person to listen to for sure. He has an accent, but I couldn’t quite catch where he said he was born. Obviously the listener has to work a bit harder to hear what someone is saying if the speaker has an accent. I found this when I first came to the south from the north. Teaching in an inner city school, I found the southern accent (think broad East Enders type accents) that the children had very difficult at times to understand and I had to ask my Teaching Assistant to translate for me on occasion, which was quite embarrassing. My ear adapted over time, but there were always rare occasions when I couldn’t understand and needed help.