Are canon SLR cameras frowned upon?

Is it kind of like how most people think macs are better than hp? (comparing canon to nikon)

Actually from what I have seen, people prefer Canon.

No, of course not. It's all about preference. 85% of my friends have Canons, which include the 7D, 60D, 600D, 550D, 5D MK2 and even older models like the XSi, 5D, even the 1D first generation. They got them mostly because of the great video. But I, as well as about three more friends of mine, have Nikons and absolutely love it, because we're into photos more than video, but would like the nice video for those special moments. The other 13 to 14 percent have pentax, lumix and olympus.

It's just like Macs and PCs. Macs barely get viruses, while PCs are much more prone to them. People like the advantage of being protected from Viruses. Some people prefer Mac interface, others prefer the way Windows Operating system was made.

I happen to love Nikons Menu System. Other like Canons.

It's all about preference. But no company is frowned upon unless they release an unworthy product.

Some of us go even more left field. I love my Sony's and there are times when I'm just stumped at some of the things they do with ease that Canons and Nikons Struggle with.

I don't know where you got the idea that Canon dSLR systems are frowned upon, but Canon is one of the two camera systems used by the pros. Nikon is the other

There have been some complaints that when moving up to a full frame Canon like the 5D or 1D series cameras, All the EF-S lenses have to be replaced by EF lenses, but that is not usually a big deal. Why? Because most people who are planning to be a pro, only by EF lenses, even if they are using cropped sensor cameras.

The other complaint seems to be that when a Canon cameras firmware is updated, suddenly some Sigma, third party lenses no longer work.

IF and only if, you are planning on shooting in low light (night football games or indoor sports), Nikon seems to have a much better performance in low light. This why many pros switch to Nikon over the past four years.

All the above has nothing to do with how well an amateur can shoot images and be very happy with their Rebel cameras and EF-S lenses.

You really can't just say that Canon cameras are frowned upon in general. That is NOT the case. There are only specific conditions when a photographer would choose a Nikon system over a Canon system