Yeah, that's a problem with petitions in general; they're really only useful for demonstrating _some_ minimum level of support or public interest in a particular issue.
They can't be used to gauge public opinion on anything remotely controversial, both because they're heavily influenced by selection bias and because it's much harder to express opposition to a petition than it is to express support.
They can't be used to gauge public opinion on anything remotely controversial, both because they're heavily influenced by selection bias and because it's much harder to express opposition to a petition than it is to express support.