While the system in the UK (where this petition is being made) is far from fool-proof, there is an attempt made in law to minimize animal suffering at the point of slaughter. Now my point is not to argue that this is successful (because it's often not), but rather to note that Kosher/Halal charceuteries aren't required even to make the effort.
In theory, the "one swift cut" method used is supposed to be "humane". In practice, it often leaves a cow struggling and writhing, suspended from his rear legs, while he bleeds to death, a time that can be up to 2 or 3 minutes.
I don't know anything about the creators of this petition, and I generally think that Internet petitions are a waste of time. However, to jump on this petition as being anti-Semitic, anti-Muslim, or whatever is to assume facts not in evidence.
The ones I pity are the ones who never stick out their neck for something they believe, never know the taste of moral struggle, and never have the thrill of victory. - Jonathan Kozol