I know, I had a male beta in my 46G for years and he never bothered any of the other fish.
Not the same beta as the one that ate the shrimp, he was a bit of a bully.

For a while I had a beta in every room in the house.
Now I don't keep them since I travel so much and the wife won't change water.
Only feed.
So it wasn't fair to them so I gave them to a local hotel that rented them to the guests
for $2.00 a night and the manger feeds them.
all the proceeds goes to a local no kill shelter.
Last year they collected over $400.00 and all of the fish are over 3 years old.

Here is Fred He was the most laid back beta I have ever owned.