The main argument against group selection has always been that, well sure, it would be nice to have a group of cooperators, but as soon as you have a group of cooperators, they're just going to get taken over by free-riders, individuals that are going to exploit the hard work of the others.
El principal argumento contra la selección grupal siempre ha sido que, claro, sería lindo tener un grupo de cooperadores, pero tan pronto lo tienes, simplemente serán dominados por oportunistas, individuos que explotarán el arduo trabajo de los otros.