Why should it be a bigger concern? Or a concern at all?
"
Occasionally
I'm callous and strange."

A bigger concern should be the fact that Igrayne is played by the director's daughter!

The scene is allegorical, not literal. The armor and raging fire in the background are elements of Uther's power and passion. The Duke is penetrated by Uther's spears just as Igrain is penetrated by Uther, and then the Duke dies at the moment of Arthur's conception. It's visual poetry, not realism.

I thought that the scene where the fully plate-armored Uther had sexual intercourse with the naked Igrayne was ludicrous when I saw the film on its original release, and subsequent viewings have never changed my feelings. I was surprised at the time that nobody in the London cinema laughed or even tittered - perhaps they were all stupified into incredulous silence, as I myself was. It was probably the 1980s cinematic equivalent of watching a 2016 Donald Trump rally on TV. ('Can That Be Real?!') It dismays me to think that I've seen some audience members laughing at things in other films that were far less risible, or not laughable at all in my opinion. Attempts to rationalise it simply don't work and can't excuse it. I can even understand the poster on another thread who says that he and a friend laughed their way through the entire film, although I couldn't have joined them. I think that there are a lot of good and praiseworthy things in the film, in spite of all its faults.
That was only one of several things in this film which prevented it from being the classic that it could have been if it had been handled with better judgement. But it would probably have required a Western
Kurosawa
to do that. John Boorman came fairly close, but not close enough.

P.s. no way should this have multiple 10s!