Don't know where you heard that but I have always read that they make great tank mates. Corys are extremely docile and passive fish. I have bronze corys in my 70 litre tank and peppered corys in my 125 litre, both with tetras and they are great. Another plus is that they both like similar water conditions as in temperature and ph as I believe they are both from rivers in South America originally.
Just chuckling at mine at the moment actually. The corys are snuffling around in the sand looking for food and a couple of the neons are hovering over them watching curiously. lol