There should be the ability to vote against petitions on this site so that people not only get to see how many people agree with a petition enough to vote but also how many people disagree.
You may be interested in these active petitions
If 100,000 people agree with a petition and vote for it but millions disagree strongly there is no easy way for those millions to indicate this. Even setting up a petition saying the exact opposite does not tie the two together to allow an easy check. A simple “reject” or “disagree” option alongside the “support” option would solve this.