It is clear that Martin O'Donnell has questionable views. This has been known a long time. While it was not a primary reason for his departure from Bungie, this was noted in the context of that affair as having created some friction with the rest of the otherwise dispositioned employees.
But let's look at his music objectively. Halo 1 and Halo 2 have absolutely spectacular soundtracks. Really great quality through and through, with both the soaring memorable themes but also a good diversity of tracks with some of the more subdued tracks being amongst the best. He really nailed a great sound to those soundtracks, that was great then and is still great now.
Conversely, I don't think Halo has lived up to that level of quality since his departure. Yes, there are a couple of hits, mainly in Halo 5 such as the intro music (Light is Green) and The Trials, but there is a lot of just plain fluff, especially in Halo 4. It was not memorable to me at all for the most part.
So, yes, if he could come back to compose for the next Halo that would be great as far as I'm concerned. I don't have to like his stupid views to enjoy the music.