your freind is definitely mistaken. as 40% of people share the same blood group ( the most common one) this would limit your choices quit a lot. it is a noted trend that people are more strongly attracted to partners with radically different immune spectra, and therefore blood types. this is the basis of the stranger effect, where foreigners visiting a country tend to get laid a lot.
The yanks used to insist on a blood test before marriage to guard against consanguinity but i never quite worked out what they were testing exactly as this was way before dna testing.