I was the same age as the young Losers when I first read It. I was shocked, I suppose, but not really offended. I identified with those kids so damn much, and, I must admit, was a little bit in love with Beverly by then, so the scene seemed kinda natural (still, though, all six of them? Ye gods.) Those cats had been through so much, had seen so much horror and death, they weren't children anymore. Their innocence was gone, and how better to illustrate this then with...that scene. (still...all six? Yeesh.)
These days, though, I look at that scene and am amazed it even made the cut. What the hell, Tabby? You asleep at the switch that day? It's rather embarrassing, and more than a little creepy, and a definite indicator that Uncle Stevie was ingesting wayyyy too much cocaine. But what could King do? If The Dark Tower taught us anything, it's that Stephen King really isn't in control of these stories, he's merely the terminal through which they flow. It wasn't a conscious decision on his part, I don't think. That's how the story played-out in his brain, and by God, that's what he put on the paper. To do less would be cheating.
Still, though...all SIX? Yeeeesh...