The person you are replying to said it’s fine in a “best friend”-relationship, implying it can be problematic in more intimate relationships. You then said that the person in question is “the son’s best friend though”, which can be interpreted as “there is no potential for a more intimate relationship” in the context (as in male-male friends can’t be more than that).

I’m just telling you how it can be interpreted and where the answer is coming from.