[blaser-waffle]

"Do unto others what gets you paid."

Come up with something concrete -- numbers / stats, or documented vulnerabilities, or well known failures, etc. -- and costs related to those. No one cares about issue [X] until you explain it to them that it'll cost [Y] to fix it later.

Then document their answers, make it clear you advised them for/against something, and then do whatever they're paying you for. If they tell you to put a toilet in the kitchen, and they're adamant about it, they can have their kitchen-toilet.