People having different opinions is normal, but not all opinions are thereby valid. Promoting genocide or child abuse have a deleterious effect on people in the in the respective target groups and so we sanction such opinions because of their demonstrated harms that result from their implementation.

The problem is how people define and extrapolate what constitutes promoting genocide or child abuse is often erroneous.

For instance: some people consider anti-vax sentiment to be child abuse, but dont consider cross-sex hormone injections for young children to be child abuse (and vice versa).

Another example is how many consider the swastika to be a symbol of genocide, but give a free pass to the hammer and sickle -- even though both of these symbols' ideologies have been similarily genocidal.