Laws do exist which separate free speech from hate speech. So if you're considered to be inciting violence, inciting racial hatred, inciting terrorism etc then you're no longer protected by your freedom of expression. Other countries like the US have different laws, in some European nations I know that on certain topics there is very limited scope for discussion.
However, there are obviously differing opinions on what qualifies as 'inciting racial hatred' for example, so it's not that clear cut. Some people would argue that Ben Shapiro incites racial hatred by suggesting that African Americans accounting for a disproportionate number of crimes is due to a problem with black culture, rather than racism. It's really not always so easy to decide what falls in to which category, hence why you get no platforming etc. People just can't really agree on what is acceptable to discuss.