I can't believe some of the responses on here. YANBU, op and @Brefugee , I'm 100% with you.
Not camping, but we took DS, who was 1 at the time on his first foreign holiday. He slept wonderfully at home, but the combination of the strange environment and the climate meant for a very unsettled first week. The couple in the next hotel room to us (also Dutch, incidentally) were very understanding but after the 4th night of him waking up and crying in the middle of the night, I sent a bottle of wine to their room. It would never have compensated for their disturbed sleep, but I hope it sent a signal that we were trying our best.
I frequently took him outside at 5am and walked around with him in the buggy when he woke early because, even as a parent, I hadn't completely lost touch with the reality of how it feels when the behaviour of other people impacts negatively on your experience - even if it's a child who 'can't help it'.
We've also eaten out exclusively at child-friendly places, never taken him to quiet places until we could absolutely guarantee that his behaviour wouldn't disturb others. I thought that was pretty normal, but it appears that families are 'entitled' to do whatever the hell they want to the detriment of others and kids have a 'right' to ruin everyone else's enjoyment. Makes me wonder why I bothered.
Back to the topic - the people with the screaming child need to leave. They're taking the piss.