I agree with your statement that Griffith is often forgotten, or simply ignored when it comes to humanist directors due to his more controversial films (which definitely seem racist, imo). Like wpqx I think he definitely belongs next to renoir and Kurosawa, though!

I've seen about a dozen of his early shorts, most of which were remarkably good. I liked The unchanging Sea (1910) the most because of its beautiful photography and its pacing, even though the direction was a tad bit too melodramatic at the end, as is often the case in many films by Griffith. A Corner in Wheat (1909) was also remarkable. What I like about him is that the acting is also quiet subtle at times (of course there are also expressive bouts), at least compared to some other films from this early period of cinema. Griffith is imo a very good director when it comes to actors. 

It's true though, that his films tend to merge somewhat in memory, as the styles and stories are often very similar.
But I still vividely recall the stunning images he conjured up in An unseen Enemy (1912), when Lillian and Dorothy Gish are on the run from the housekeeper who tries to kill them. The image of the hand with the gun sticking through the door is terrifying and haunting! 

From the films you mention I've only seen His Trust (1910). I wouldn't call it racist, but it remains very ambivalent. While Griffith clearly isn't portaying the slave as a negative figure (quite the opposite) his view is simplistic and condescending, not so if you watch only this film, but if you are aware of the fact that he uses this view of black people over and over in many of his films. Of course some of the people surely had been naive, and loyal to their "masters" but the majority probably wasn't. Talking about the times the film was made in doesn't make it much easier to watch.
It's interesting that almost all black people were portrayed by whites in blackface in American films up until the mid 20s. This wasn't something one should particularly blame Griffith for. To me it's rather a document of its time, similar to the fact that men had to play female parts at the theater in Britain during certain periods. Like in ancient Greece and in Europe during the middle-ages women weren't allowed on stage.