Keeping same sex rats together.

It makes me completely furious when I see an "owner" who has males and females together. I recently seen an ad on cl and they showed 4 females with 3 males in a tank with a topper. That is hardly big enough for one rat, let alone 7.  I am concerned how they will cope with so many babies. It is beyond me how one can think this is acceptable. It is not a secret that males and females will reproduce. It is just beyond me how they can sit here and not even think about that.