One of your links says Sag A is a quasar. Another says Sag A is the Black Hole. It justs shows that although a few people have a few theories about it, no one knows with anything approaching certainty what is there.
No, it's not obvious that there is something of huge mass. Obviously there is huge mass towards the middle, but nothing to say it's a single entity. Why can't it be lots of stars orbiting each other very very fast.
Why don't you like people calling everyone stupid? A lot of people ARE stupid, and the number of stupid people increases every year. To deny that 'the masses' are stupid would be to assume that everyone is clever and intelligent, something that any newspaper would dispel in seconds.
If it was obvious, why hadn't Black Holes been 'invented' 100 years ago? And why do a lot of respected scientists even deny their possible existence. Sure, a lot of it is caused by people not liking change, but even then there is less weight behind the concept of Black Holes than there should be in this day and age. Nothing is certain, and a BBC Learning Show has almost no authority on the subject. I don't claim to either, but I recognise that Black Holes are still mostly theoretical in nature. Who's to say the theory is wrong and there isn't a giant Christmas Cake in the center of the universe?