I think he's just saying it in reverser order:

よしな　くだらねえなぐりあいなんぞやるのは！

Reversed becomes:

くだらねえなぐりあいなんぞやるのは よしな！

or in more formal Japanese:

くだらない殴り合いなんぞやるのはよせ！

On a side note, from what I've read, the old's man's style of speaking might a more of a dialect where くだらない becomes　くだらね and　よせ becomes　よしな.

Other examples I've seen of this slang are: 面目無い　→　面目ねえ 食べろ　→　食べな

Interestingly I've only seen this speech style from old men.

I think he's just saying it in reversed order:

よしな　くだらねえなぐりあいなんぞやるのは！

Reversed becomes:

くだらねえなぐりあいなんぞやるのは よしな！

or in more formal Japanese:

くだらない殴り合いなんぞやるのはよせ！

On a side note, from what I've read, the old's man's style of speaking might a more of a dialect where くだらない becomes　くだらね and　よせ becomes　よしな.

Other examples I've seen of this slang are: 面目無い　→　面目ねえ 食べろ　→　食べな

Interestingly I've only seen this speech style from old men.