The petite bourgeoisie as a whole has bourgeois aspirations and most will likely act against the interests of the proletariat, but I’ve never heard any communist seriously claim that they need to be executed (although it depends to what degree they fight back during a revolution; if they try to retain their capital through violence, it will have to be violently expropriated). They will need to be re-educated for their new proletarian role, and the feasibility of doing so depends on many factors, but there’s no need to kill someone who doesn’t resist