Serbs indeed have majority of slavic genetic tissue, according to the researches conducted during years unlike Bosnians and Croats however my opinion is that language doesn't determine the origin , though it determines only circumstances under which population in particular was at particular time, and therefore used to build certain cultural background but not the origin.
Why is so matter whom Slavs, or not. Somebody told me Titos era Yugoslavia would not questioned those matters. Why is so important to know what genetics we have.
first point:well if we want to consider that as a fact, we have to consider it from the point of genesis. genesis is being proved scientifically and via genetic tissue of the population,or majority of the population. based on that, there have been many scientific proves that bosnians and croats are not slavs. second point:language on the other hand, is variable that can change throughout time, however time that passed was not enough to effect the genesis of the population and it represents an origin myth. it used to be reinforced by the socialist government as a factor of reunion and prevention from secession and it was effective when it comes to peoples mind. though people accepted it since it was way to unify and accept easier that the 'other' one is not really the other one but he/she is 'ours'. finally, I don't find any point wrong as long as it is being emphasized on what basis that particular point is being made and as long as it is correct.