I exect that's the anti-anti-vaxxer bill: clearly, it is there to apply to coronavirus measures, and the only reason to not want to comply with the law is if you want to walk around and potentially infect other people. There needs to be a legal basis for the government to not let you do that, and this bill is it.
The opposition can be reasonably based on these lines of thought:
a) it's my right to infect others (but it is others' right to not get infected by you)
b) the government can achieve this end through other means (how?)
c) the government can abuse this bill (given that it is tied to the coronavirus pandemic, I doubt that would pass judicial review)
It is a difficult discussion to weigh these restrictions against our civil liberties guaranteed in the constitution, but overstating cases does not serve that. Nobody becomes "property of the state" (don't see slavery in there), nobody is denied access to the judiciary (there are limits on how long you can be detained for assessment, for example, measured in hours), and the usual procedures still apply; and yes, your decomposing body can be cremated if a burial is not possible and it becomes a health risk to those still alive.
It does not help the discussion if you assert your right to infect others, and the right for your corpse to rot if it can't be buried; which is what this petition effectively does. The government gets rights it does not usually have, but they are tied to a specific purpose (which the petition takes pain to mention as little as possible), and the democratic judiciary is our guarantee that they will only be used for that purpose.
If there is discussion, it ought to be about whether the measurements are reasonable and effective and proportional to the that; that makes sense; but that petition does nothing to bring that about.
If you're an anti-vaxxer (or believe this pandemic is a hoax), you will oppose this unconditionally, but the majority overrules you because it values its health, and rightfully so. I see nothing wrong with that.