Well it's more along the lines that just because you don't like something doesn't mean it's bad. Personally, I'm not partial to 4E. Why? I just didn't really enjoy it for a lot of minor but appreciable reasons. However, I can see the ways it was good; it presented some much more visceral approaches to 3E mechanics, it simplified a lot of things, it brought a lot of otherwise "boring" classes like Fighter forward and into the spotlight in non-traditional ways.
Things CAN be bad, but part of having an open mind is appreciating that people like/hate different things in different ways. The things I dislike about 4E might be things somebody else likes. And as an adult human being I can empathize with other people and understand why they might like "thing X" that I dislike.
Of course, though, as I said things CAN be bad. /tg/ pretty much universally reviles FATAL as an actual system (though we find it absolutely fucking hilarious, since... well, "roll for anal circumference"?) which is something. Things can be bad, it's just understanding that our bad isn't someone else's bad.
More to the point on the other dude's shenanigans though is that if a system has appreciable qualities, they can be fixed or used elsewhere. Lots of 4E's stuff can be salvaged or homebrewed or modified somehow. And that's pretty cool! I tend to run Pathfinder and, when I got a request to make a more interesting Fighter variant, I looked to the 4E handbook. I didn't use the content there exactly, but it was a great source of inspiration.