I'm sorry but i guess there is no kernel parameter to disable ppp. If the driver was compiled as a module, not built-in, there's a possibility to disable it in the parameters but it only depends on the system's boot scripts. I don't know for redhat if there is a parameter to disable modules.
You can however manually disable a module if a module doesn't load before having the bash prompt by doing a single-user boot.
Highlight the kernel to boot from and press the 'e' key.
Find the line that starts with 'kernel' and press the 'e' key again.
Move to the end of the line and add the option 'single'.
Press enter to save changes.
Press the 'b' key to boot with the new boot parameter
If you successfully made it to the bash prompt, change directory to k/lib/modules/<version>/kernel/drivers/net/ then rename all ppp modules there. e.g. ppp_generic.ko to ppp_generic.ko_.
You can also blacklist a module if your system supports hotplugs by adding the module's name to the file //etc/hotplug.d/blacklist. e.g
Code:
echo ppp_generic >> /etc/hotplug.d/blacklist