This has been fixed since Fedora 7. If you specify no options, the defaults are DHCP for IPv4 and auto neighbor discovery for IPv6. Previously, if you disabled IPv6 during installation or selected auto neighbor discovery, DHCPv6 still occurred.
Fight the temptation! Admit the truth to your users - you're a loser, FooBar just sucks and ate their email. ;-) This feature should be fixed, not made optional."
This entire thread was a perfect example. It isn't a question of whether or not to enable IPv6; if we want IPv6, fix the bugs that adding it introduces. Don't add options to enable it or disable it.