This article aims to understand the (un)reasons that justified the ban on blood donation by men-sex-men (MSM) and their partners for 12 months, which, in practice, did definitively, based on the theses raised in the judgment of the ADI 5543/DF at the Brazilian Federal Supreme Court. The methodology used is developed from exploratory research, as well as content analysis, considering the need for checking any constitutional (in)compatibility and (non)conformity, veiled in the forms that cover the interpretation activity of the Brazilian Federal Supreme Court, in the light of the reflexive sociology. It concludes that the prohibition of blood donation by MSM is not supported when faced with the principles of proportionality and reasonableness, in addition to being a serious disrespect for homoaffective human rights.