Hmmm thats a tough one… Im no expert and i dont know your son but it can be geniune. Alot of times im doing something and my parents/teachers dont know and then they say something like that (a comment on something wrong im doing) and i just want to rub it jn their faced like “oh ya im so bad….well i just stopped soung xyz” it takes a lot to stop myself but i dont really like saying stuff like that since all that matters is that Hashem knows and i usually dont say anything… But i know the feeling and it can very well be sincere.
Just daven it is and try not to make comments like tht (and yeah its hard- even for myself amonsgt friends i have to be careful not to make preachy comments because i know how hard it is to hear them)