Most people always think that if pokemon were real, their would always be tyranitar or something blowing up cities and everyone dying. However, this is near impossible.
1) Pokemon like garchomp and salamence are extremely rare. Their final and second evolutions are almost non-existent in the wild, whereas their first forms are only found in secluded areas.
2) Even if something like this happened, which is very unlikely, the police type people would have their own monsters to counter the monsters with. Moves like sleep powder and thunder wave could also be used. People more often than not think about what would happen when the 'bad guys' got pokemon, but they forget that the lawful people would have them as well.
So really, the bad would be balance out by the good so as to make things more or less the same, just on a larger scale. Also, having a cubone would be nice ^^