OK, I was leaving this thread alone, but I think a little historical background is needed here.
First, in the Victorian era, there was no concept of "gay" or straight as we know it today. No one would really have ever identified themselves as such, it never would have occurred to them to do so. "Out" as a homosexual was something a Victorian person would not have even understood. The term homosexual did not even exist in 1895.
It was the duty of all men "of a certain social standing" to marry and father children. Now, it was common that many such marriages were simply for the sake of appearances. Husbands had many mistresses (like Edward, Prince of Wales) wives knew, and often had lovers of their own. Husbands did have male partners too, it simply was the way things were. The "lifelong confirmed bachelor" who lived with a "close friend" was common (look at Sherlock Holmes and Dr. Watson). Many many young upper-class men had male lovers and intimate male relationships at University; there was nothing really new or scandalous about the world described by Evelyn Waugh in "Brideshead Revisted". These men simply "grew up" and married. Public overt homosexuality was frowned upon, and illegal in England, but most people simply did not CARE what was done behind closed doors, so long as discreet. Oscar Wilde was tried in court and public opinion not so much because he was homosexual per se, but because he was quite public about it.
In Germany, male homosexuality was illegal under Article 175 of the Prussian Code (tho not female!). However, one could only be prosecuted if the police actually caught someone physically in the act. The German Court was filled with homosexuality, known full well to the Kaiser, starting with his close friend Furst Philippe zu Eulenberg.
Should a possible bisexual or homosexual nature of Grand Duke Ernst be discussed? Yes, as one can not fully understand the nature of the man in order to explore his motivations and feelings. HOWEVER, I agree fully with Greg that the man's achievements must not be colored or judged by this aspect of his life, and far more importantly, one CAN NOT and MUST NOT impose 21st Century beliefs, morality or values on the behavior of someone living in the 19th or early 20th century.