While I do understand the differences between the EU and US attitude towards TV content I am amazed the front desk didn't have the ability to lock out these channels from the room. This is most certainly not a european only thing, I've seen many hotels in the US offer a "free" 20 second preview before switching to the room number page. It all comes down to the parents being responsable for what the kids do.

What you could do is write to the hotel and advise they update the system so it can lock out these channels from room with kids, I doubt writing to Hilton will help but it certainly won't hurt, perhaps it will trigger some kind of chain-wide policy on the matter.