Every kind of trading is risky. Bitcoin has a very small market cap, so fluctuations are frequent. Bitcoin is often considered one of the most attractive currency for trading, due to high volatility. But there can be a risk of scams and fraud. So choose wisely.
I would only agreed on you that trading would only be risky if traders don't have enough proper knowledge in doing trade. But if you know the process of doing in the trading platform, well I guess the world "RISK" I think has no space anymore. But the risk that they are talking about for what others said here, if your prediction is wrong, everything you had for sure will disappear at once in just a matter twinkle of an eye only.
Even experienced traders that have been in the game for years still risk their money. There's no such thing as no space for risk anymore because that would mean that you're sure with every single trading move that you make.
Actually, it's easy to know the whole process of trading. You can also know the strategies to earn profits. But the thing is, will the market go in accordance to what you wanted? It's all random if you ask me. There can be a huge dump coming up and no one knows about it except the dumper himself.