Googling pictures, that is how some get their info?

Slings: Take a closer look at the top pic, to the lower right of the optic. Sure looks like a single point sling. Pic of the Aussie sitting, notice the sling hanging from the weapon?
Yes, some units have an SOP against slings just as some have an SOP for slings. Six of one.........
The sling has come a long way since the days of the dinosaur. Most seem to think of the traditional over one shoulder or across the back sling method. Single points, three points ect. are a little different. There are many reasons not to use a sling, and there are more for it. Some is unit policy, some is individual preference. In my military days slings were a no, no for ruck marches. That was for two main reasons. One, to develop good habits as it relates to "at the ready" position. Second was simply to toughen soldiers up. At no time during actual missions, deployments or any of the like were slings prohibited.
Slings were needed for evac., CQB, RTOs, rappelling and fast roping, ect. Try moving your buddy, your weapon, and his weapon without slings. Not unless you have octopus arms. Weapon transitions are possible but more difficult without a sling. This is where single points or three points (my pref) come in. There are many situations where you need one or two hands, but do not need to transition to a pistol. Once again a sling comes in very nicely. The overwhelming usage of slings is some type of "patrol", "assault", "cqb", "tactical" or what have you. weapon in front at the ready. Not to say that you do not have your hands on the weapon, butt stock up at the firing shoulder ect. Just that you have the option. It has been said by many that a sling is to a long gun as a holster is to a handgun. Use it if you want, don't use it if you don't want to, but to not have one at all is limiting your options. Limiting your options can often set you up for failure.
Sights. Yes, I have read Haney's book (re-read that section and tell me if he actually states or advises NO SIGHTS or if he is just talking about "instinctive" drills), and yes I too know many men still in the service, yes many are "operators" although most I know including myself do not personally use that term. I don't want to get into an "I know this guy or that guy" argument or a "my daddy can beat up your daddy" argument. I will say that I am currently still in the business and can give personal observations as well as personal preferences. Let me stress that training is just that. Yes, many men have removed sights from pistols. This forces you to learn instinctive or point shooting (whatever is the cool term of the day). But that is were it stays, at the range or shoot house.
You don't have to leave the sights off the weapon to be able to use instinctive shooting tech. My personal preference it for the "flash sight picture” of the front sight only. At close range this is extremely fast, and still very accurate. At CQB distances you are watching the threat, not the sights. So when the front sight post enters you vision (and you still have your focus on the threat) you pull the trigger. Much different than bulls eye shooting but still somewhat aimed. I also darken the rear sights with a Sharpe marker thus making the front sight more visible.
There are several problems with no sight. Some of which are:
At increased distances your shot group will spread. No matter how good you are on the range.
A HUGE one is liability. Yes even "operators" have some degree of liability no matter what Hollywood says. Oops, just shot the hostage, POW, fellow officer, team mate ect in the face!!! Sorry!!!!
No PD is going to allow its officer to carry weapons with no sights. None, nada, no way. (See Liability) If you SWAT buddy can produce an actual policy letter on letter head I will offer my sincere apology, until then it is “internet legend”.
Nobody I know (self included) will ever work with someone who has no sights on a duty weapon. Let alone go in a room with them. Like I said before I don't doubt that you buddies have trained with taped or removed sights. Many of my team members have done the same. It just doesn’t happen on actual ops.
I know this last part is going to chap some asses, but I have to believe that a lot of individuals on internet forums are either armchair warriors, poorly trained, or simply so far removed form the “been and the bullets” that they are out of touch. IMO