with yum how can you remove a package but not remove its dependencies at the same time?

Appears possible, by using rpm:

$ rpm -e --nodeps packageA

though obviously be very careful, since if you remove a dependency package and don't put it back that could lead to unexpected results for the packages that still depend on it...

I found it was possible to do this with yum like so:

sudo yum remove --noautoremove <package name>