Point is Dumbledore is homosexual and he WAS in love with Grindelwald. It is however not revealed if Grindelwald returned Dumbledore's affection or even if Grindelwald was homosexual himself as well. Many mistakes Dumbledore made while with Grindelwald were partially because love is blind... Now it was also because his own brilliance made him arrogant. Rowling did reveal that Dumbledore was homosexual.