First of all, in a lot of your earlier posts you have been accusing people of doing rude things, and in the way you have been doing it, it sounds more offensive than what they're doing in the first place. Second of all, they were stating their opinion, and you really can't blame them for saying something as simple as "no" when threads with the exact same or similar ideas have come up dozens of times in the past. I don't think they were doing anything wrong. But since you seem so intent on having this added to the servers, I'll give you as full of an explanation I can make on why it shouldn't happen.
Teams are annoying for everyone when you aren't a part of the team. They are harder to kill, and can simply be unfair if it's just you against multiple other people that aren't going to purposely hurt each other. Though you are suggesting this for just 2 people, a team of 2 can be just as overpowering as a team of 10.
This addition to the plugin would remove a very important aspect of the survival games, and the favourite of many people. Betraying. If people are nagging you to do this command with them, then you either do it and can't kill them, or you don't do it and you aren't actually teamed, and the person who you would otherwise be teaming with won't trust you. You shouldn't trust the people that much anyways, but without this command it can still exist.
Also, what about flint and steel? It's impossible, or at least not worth the effort, to make it so that when someone places down a flint and steel, his teammate can't get hurt by it. The same issue might also exist with bows and arrows. So if you can still hurt them as long as you're not using your sword, what's the point?
Sure, there are some advantages. It makes teaming easier, you don't have to worry about hitting your friend by accident, and you can be assured that you won't be betrayed. But is that really worth it?
Something like this would be more of a hassle than it is a benefit. Every game you would have to do the command, and it would get tedious and annoying. It's probably not worth the effort of coding it.
Oh and i forgot to add this to my rant, but if your just one of those people who goes from topic to topic looking to boost there messages, how sad are you. Honestly at least leave a humanely response with at least the logic of a 6 year old. Thanks!
On a final note, you can use the edit button if you forgot something in a post. Posting more than once in a row is against the rules, so please avoid doing it in the future.