I would agree, but the courts have consistantly disagreed with that position for decades.
Be that as it may, that does not change the fact that we are right and the Courts are wrong. :-)
The way I interpret the First Amendment, the Free Excercise Clause does allow the public display of overtly religious symbols such as a Nativity, a Menorah or a Koran as long as no religion is specifically prohibited.
Once the Courts take it upon themselves to declare that a Menorah is "secular" and allowed but a Creche is "religious" and needs to be excluded, that crosses the line into arbitrary judicial tyranny that the Founding Fathers would be appaleded at.
Common sense dictates that Nativity Scenes, Menorahs and Korans are religious symbols and that Christmas trees, Santa Claus, dreidels and latkes are not.
The religious nature of the display isn't really the issue. Sea-Tacs contension that the Holiday Trees aren't religious whereas a Menorah is wouldn't have held up. The real problem they would have faced in court was barring the Menorah while allowing the trees, which have a religious component regardless of what Sea-Tac says. That's borne out by the outrage by Christians on this site over the removal of non-religious Holiday Trees.
BTW, a Creche is OK in public displays and is making a comeback, partially due to the inclusion of Menorahs. It all depends on the nature, and inclusiveness, of the displays. Note the link in post 145.