Digging a little, I found out that there used to be an issue where people could (accidentally or intentionally) admin-delete these altars (as well as some other in-world crafting stations such as the Frost Smithy) from the world, and they could not be replaced. Maybe whatever checks Funcom put into place to prevent this also prevents admin-spawned altars from being blown up.
I suspect that thing isn’t meant to be placeable even in admin mode.