There has been so many posts relating to this, you should direct your point to YouTube as it can be accessed on very many devices and all with the same standard of parental control, virgin is a platform for programmes and apps therefore can't be in control of the individual companies, e.g. sky cinema require a pin for thier content which they have put in place.
I think this needs to be addressed by Virgin especially with the high profile nature of the Momo Challenge.
Parents need to be able to choose what channels and apps can be accessed through a service and companies need to take responsibility to ensure children can be protected from content when viewing it in their own home.
It appears you can lock the YouTube channel but can’t lock the app.
Surely this is a simple fix and something that Virgin should take ownership for making this change happen to improve parental controls.