[CentOS] SELinux on CentOS-6.6

I wish to reuse ports 80 and 443 for a different service. When I try to assign the port context for that service I get this:

/usr/sbin/semanage: Port tcp/80 already defined

When I try to delete the assigned context then I get this:

semanage port -d -t http_port_t -p tcp 80 /usr/sbin/semanage: Port tcp/80 is defined in policy, cannot be deleted

httpd is not installed on this host. But looking at the port context assignments I see this nonetheless:

semanage port -l | grep ^http_port_t http_port_t tcp 80, 81, 443, 488, 8008, 8009, 8443, 9000

How do I rid myself of these artefacts and make the context assignments that I wish?