I have not heard of any high school coach hurting a player's chances on purpose. I do imagine that there are some that have given their POV and that might different than the parent/player POV and that could be viewed as being hurtful.
In your case seems like you have some respected knowledgeable people giving you advice that your son has the ability to play college ball, so one would imagine that your HS coach might see it the same way. However sound like you have some concerns about that. I would think leaving his HS coach off might raise some red flags? I know my son’s high school coach has been contracted by several schools that have interest and has not been contacted by others that have also shown an interest.
So I guess it depends on the college coach. I was told at a recruiting seminar that College coaches as a general rule do not pay that much attention to HS coach recommendations. Like I said our experience has been mixed, some have contacted the HS coach and some have not.
Has your son talked to his coach and asked for his help? Asked him for recommendation? Might help you decide if you want his as part of the process? My son’s HS coach has been very helpful