IMO if you don't use any service requiring that port (like some 3rd-party web-server apps) there shouldn't be any problem with closing it for incoming connections.
@GG_jr is right about port 80 being used for updates (yum). So it must be kept open for outgoing connections (for external repos).
As the port 80 is coupled with port 443 for httpd network service you may create a new firewall object service for port 80, and use it when creating the new firewall rule (eg. drop - red to any - http80service).