Ignore Moonlighty. Moonlighty has an awful reputation on these boards for posting obnoxious, mean spirited responses. While I am sad these boards are going away, at least it will mean no more Moonlighty.
I agree. Barney uses the Bro Code when it benefits him. A true "bro" would have known that sleeping with his so called best friend's ex is a no-no. It is an unwritten rule that women also follow when it comes to their best friend's ex boyfriends. Obviously there are expect ions but I don't see that here. The whole Ted-Robin-Barney triangle was boring.

Bullsh!t. I never said he "owned" Robin, but I'm just pointing out the hypocrisy of:
1.-Believing Ted was a bad friend for going after Robin after what? 20 years after their divorce? Plus, Robin had clearly always been in love with Ted, but was too selfish to never admit it (she wanted to run away with Ted the day of her wedding, I mean wtf)*.
2.-Believing Ted was a bad friend when Barney had done something so much worse before that. It was even wrong according to Barney's own "Bro Code".
*
I'm aware this is yet another example of HIMYM's bad writing. I'm just mentioning it because we're talking about the show.
So, according to your own words, there's nothing offensive to Barney about two consenting adults deciding to be together when he isn't currently married to either.

Well seeing as Robin isn't Ted's property, there's nothing offensive to Ted about two consenting adults doing things when he isn't currently dating one of them.

Consider the daffodil. And while you're doing that I'll be over here looking through your stuff.

It's funny you think that way, considering Barney had sex Robin, who was the ex of the person he considered to be his best friend. Barney was a terible friend more often than than Ted. It's even implied he had sex with Ted's mom.
I think all five main characters acted like dicks every once in a while.

To be fair, Barney's way of trying to be Ted's best friend usually involved Ted having to do something that was outside of his nature. And remember, Ted planned on moving to Chicago for a fresh start in part to help give Barney and Robin a chance.

He didn't go after robin until they had been divorced for like 20 years.

Ted and Robin never had anything simple except him trying really, really hard to get her to go out with him.

Consider the daffodil. And while you're doing that I'll be over here looking through your stuff.

Robin went after Ted too.
In a deleted scene available online you can tell she clearly still wants Ted.
And just because its not shown on TV we can assume Ted asked for permission and even if he didnt Barney realised he isnt made for marriage and knows that Ted and Robin always had that special something.