The generally contrived nature of this argument aside, this is really just revisionism. Commodus was 18 when Aurelius died, and he didn't become a lunatic until a fair bit after his fathers death. If you're looking for flaws in Marcus Aurelius (there's plenty), this isn't one of them.
It's easy to get swept up in Meditations, viewing Marcus as the stoic Philosopher King that has profound lessons for us even today.
Parent tried to remind everyone about Commodus, and in my opinion correctly so; if Marcus lived up to the myth surrounding him, he'd have intuited the situation and dealt with it.
But he either didn't see what was coming, or decided to do nothing. Because for all the hype, he was just a man. Keeping this in mind is an antidote to getting carried away by what is a genuinely compelling piece of writing.
I wouldn't make this argument in a vacuum, but I saw OP get downvoted and wanted to jump in because I thought it was a fair enough point.
Commodus renounced Stoicism after his fathers death, and didn't do any of the terrible things he was known for until after then either.
This argument is beyond weak in terms of criticising Stoicism or Marcus.
If the argument were that weak, you wouldn't bother with the strawman to counter it.
Of course, to not hand power to Commodus would have meant his death. I'm not judging him for his decision, but given his absolute power and obvious clarity of thought, it was a conscious decision to choose his son's life over the good of the empire.
https://en.wikipedia.org/wiki/List_of_Roman_emperors