If Wikipedia is to be trusted (and in this case, their source is the FDA), there is in fact a toxin in some raw beans, such as kidney beans.
The toxic compound phytohaemagglutinin, a lectin, is present in many
common bean varieties, but is especially concentrated in red kidney
beans. White kidney beans contain about a third as much toxin as the
red variety; broad beans (Vicia faba) contain 5 to 10% as much as red
Phytohaemagglutinin can be deactivated by boiling beans for ten
minutes; the ten minutes at boiling point (100 °C (212 °F)) are
sufficient to degrade the toxin, but not to cook the beans. For dry
beans, the U.S. Food and Drug Administration (FDA) also recommends an
initial soak of at least 5 hours in water, which should then be
During the pressure-canning process beans undergo (they are fully cooked in the can), the toxin is certainly deactivated. Canned beans are ready to eat, even cold, although they probably taste better hot, and with some flavor from a sauce or accompanying dish.
The danger would be in slow-cooking dry beans of this variety, which have never been previously cooked.