Kirk went in prepared to defend his ship against a conventional threat. He had no way of defending his ship against an imaginary one, when he and his crew didn't know they'd stepped into somebody's murderous game and hadn't been informed of the rules. He wasn't about to volunteer his crew to step into disintegration chambers to go along with said game.
Why do they have to spell it out? They don't want visitors. None. Zero. Zip. Full stop. If you put up a No Trespassing sign on your property do you have to post an addendum as to why you don't want anyone there? Isn't a simple "No Trespassing" enough? They made their wishes quite clear.
I never said that they had to, that there was any obligation. I specifically said that it wouldn't have hurt
Your arguments seem very informed by 24th century, politically correct Trek. That crap didn't fly in Kirk's time.