When people say that things are not equivalent it doesn't mean that they are excusing either or any of the things being compared. It's just that they have nothing to do with one another.
It's like when people say that a 16 year old should be treated as an adult if they commit a crime because they are allowed to marry or join the army. Those things are not the same and were arrived at in different times and for different reasons. It doesn't mean that the age of criminality is right or wrong, or that the age of marriage/joining the forces should or shouldn't be adjusted - just that one doesn't justify or excuse the other.
To me, comparing incitement to riot and murder is dreadful and so is viewing child pornography. Those who justify them can say 'it's just using words', or 'it's just looking at pictures', but the law (IMO rightly in both cases) sees both things as far more serious than that. They are different crimes, with different consequences. And in times of civil unrest, just as in wartime, different rules apply. Jailing the inciters doesn't mean that HE should or shouldn't be jailed.
FWIW I think he should have been, but legally the situation is that he couldn't have been. Maybe we need to look at sentencing around pornography. But if we do, it shouldn't be based on sentences for rioters or inciters to riot, but considered in its own right.