Agreed.You can still do that, but by looking harmless and showing "no balls" as you put it, you get them to talk more and possibly incriminate themselves some more. Once you raise your voice, you are in for a fight. Timing is everything and you need to pick your battles wisely.
The old saying... 'you'll get more flies with honey than vinegar'.
Also agreed ... once you start the fight... the fight is on... and walls will go up... people take sides... people stop listening ... those not wanting to get involved will avoid you etc... you can always pick a fight latter after you start off polite and meek if that is what you choose to do ... but you can't always go back to polite and meek after the fight is started.