Well probably you are right. It was not a genocide but killings were on a "genocidal scale".
Let's also mention the massacres (including pogroms of Jews) carried out by Khmelnytsky's rebels in 1648 and following years.
But it was also not "a genocide proper" - they murdered Jews not because they were Jewish, but because Jews were servants of Polish and Ruthenian magnates, and Cossacks + some of the local Orthodox peasants who supported them hated those magnates (and their servants).
so much as eliminate the state's resistance to foreign occupation.
At the beginning the arrival of Charles X Gustav of Sweden was not perceived as a foreign invasion by many Poles. He was considered as a claimant to the Polish throne - and many would like to see him on the Polish throne, because they considered John II Casimir Vasa as an inept king.
This is why resistance to Swedish "occupation" at the beginning was negligible in many areas.
Many cities and even a few entire regions (e.g. Greater Poland) opened their gates to the Swedish army without resistance.
Polish forces loyal to John Casimir Vasa lost a few opening battles and after that they lost the will to resist Swedish forces and most of them also betrayed to Charles Gustav (those defeats were perceived as only further confrmation of John Casimir's ineptness as a king and as a commander).
After those defeats, John Casimir was forced to escape from Poland to his lands in Silesia (he owned two duchies in Silesia).
Even those who initially supported John Casimir against Charles Gustav, mostly betrayed to Charles Gustav after this.
Only later - when Swedish forces started to pillage captured territories - people realized the fact that it was an invasion, not a "raid for Polish throne".
The fact that Swedish forces devastated many Catolic Churches and attempted to capture the Jasna Gora Monastery (which - however - managed to repulse the attackers) also contributed to the overall bitterness and dissapointment with behaviour of Charles X Gustav.
All those Swedish crimes and their barbaric behaviour towards "conquered" population contributed to outbreak of uprisings in many places of Poland (peasants played a very important role in those uprising - which means that they preferred being ruled by Polish nobility rather than Swedish oppressors).
Also majority of Polish forces (both regular forces and levy en masse) who sided with Charles Gustav, now again started to resist Swedish forces.
It should be noted that candidates for Polish throne arriving with their own armies to Poland, was not something completely new. For example in 1588 Archduke Maximilian III Habsburg entered Poland with his own army because he lost the election to Polish throne (but he still had many followers in Poland, who would like him to win the election). Maximilian was, however, quickly defeated in the battle of Byczyna by Royal Chancellor Jan Zamoyski:
http://en.wikipedia.org/wiki/Battle_of_Byczyna