There are very few left. Stanley Payne is probably the last remaining historian who casts Franco in a slightly more positive light, though I wouldn't call his appraisal of Franco "positive". As far as those arguments you heard from this person, those seem to be largely propagandistic. You'll have to clarify for me what he/she meant by the "establishment of a national language". The official language of Spain had long been Castilian/Spanish well before Franco and there had been plenty of other efforts to suppress regional language expression before he took power- his was simply the most strident.

Franco hardly unified Spain at all. In fact, he shattered it. It's true that he "unified" Spain in the sense that he destroyed practically all dissent and imposed a single, National-Catholic vision of Spanish unity, one that completely erased regional diversity, identity, and culture. But he created bitter disillusionment in the eyes of millions of Basques, Catalans, and Galicians. These were people who might have been more open to a stronger Spanish national identity had the government tried to be more inclusive. But because Franco insisted that there was only one Castilian Spain, it alienated millions of Spaniards, so that by the time Spain had transitioned to democracy, many millions of Spaniards did not identify with the central government. You see the damage today- look what's happening in Catalonia. Half the population there doesn't even see itself as Spanish. I'd hardly call that a successful unification of Spain.