That is incorrect, due to laws against discrimination in hiring and the potential for disparate impact. The babyseat example is one where there would be an obvious age bias to the policy, making it illegal due to age discrimination.
That's true: today, US law does disrespect property rights--not to mention the freedom of association. To that extent, however, it's US law that's in the wrong.
...illegal due to age discrimination.
Yup, freedom of association is much undermined. Luckily for me, soon it will be illegal for pretty girls to refuse to sleep with ugly guys. After all, if I can prove that she sleeps around pretty indiscriminately, then her refusing me can only be chalked up to bigotry against unattractive men.
Age discrimination laws are strange- you are free to discriminate against people because they are too young, but not because they are too old.