First off, I don't like your terminology of statist socialism, it seems so superflous and tainted with ideology. I personally consider myself a sort of a socialist and naturally suport basic human rights, civil rights, and economic rights. For example ownership of ones own body and self defense.
Of course self defense is useless unless you have acess to teh means of self defense i.e. guns. Of course guns are useless unless they are readily avialble on the market at a reasonable price and are of good quality. Also, the doctrine of self defense is meaningless if people have to chose between buying a gun (self defense) and buying food. So in no way does gun ownership conflict with socialist thought of any kind. Personally, I think gun training and safety should be made standard curriculum in high schools across america. I also liek concealed weapon laws and other such bills. I also like background checks and safety locks, however.
Also, don't forget the bonus effects of gun ownership: less crime, deterrence to foreign agression, and a last ditch defense against fascism.
On the matter of body ownership, I think the human right to privacy and the sanctity of the doctor-patient relationship should cover most occasions and should prevent state intervention. It is not up to any third party to determine exactly waht a peson puts into their body or decides upon as a medical treatment. Unless, of course, we are talking about minors. Also, it doesn't hurt to have products and such be labeled clearly so that people can dtermine what there ingesting and it is perfectly acceptable for a liberal democracy to ban toxic and carcinogenic substances from common use if there pervasive use endangers public health and violates personal privacy.
A side note on social engineering, most is done by private firms and corporations. What exactly is advertising if not the attempt to change the behavior of large numbers of people? Smells like social engineering to me.
Finally, what is this stateless socialism stuff? Would it work? Would anyone want to live there?