I was always having to saw off Rough Fell tup horns.
Do it with a small saw or a 'cheese wire' - tougher stuff, obviously, sold for the job.
In Roughs, they are bred from and shown - sawn off horns are no detriment to showing.
A source of considerable argument, since some of us feel as Fleecewife, but 'tight horns' also go with a massive head and solid carcass, whilst wider horns go with a much lighter, 'scrawny' body. The former is prized and so the horns are tolerated. Wrongly in some folks' opinion.
The sensible view, and if horns are part of the showing in Herdies, would be that he is not showing material, so saw off his horns for his own good. You can feel where the blood and nerves reach to - that bit is hot, whilst the 'dead' bit is cooler (easier to feel in the winter or first thing in the morning).
I have seen sheep with holes drilled through their horns, so that a bolt could be put through from one curl to the next, to train them away from the face. I can't help but think this must hurt, like braces on your teeth, and the hole gives away the game anyway.