"We either have freedom of expression or we don’t. As soon as we start to qualify it, we have lost it. Who is to decide what is reasonable anyway?"
And the obvious answer to that is "Is it reasonable to yell 'FIRE!' in a crowded theatre"?
The Right of Freedom of Expression (which is one that I most certainly support and encourage) has to be balanced with the *Responsibility* to use that Right in a sensible and non-injurious way.
You can find many posts from me on these forums and elsewhere about the right of consenting adults to produce and view so-called Extreme Pornography, but you won't find any posts from me anywhere about the right of someone to produce child pornography (and just to forestall a possible response: drawings which are entirely fictitious are of course an entirely different matter)
So that is "qualifying" the Right of Freedom of Expression, but unless you would argue for the right to take photos of children in sexual situations (and I am sure you wouldn't), you must, ipso facto, agree that there *is* a line beyond which that Right has to be restricted.
As for your analogy that the idea of objecting to those who claim they can "cure homosexuality" is akin to the Church's objection to the Copernican System of Planetary Motion, I am sorry, but that is complete nonsense.
The former is not an "illness" and to claim this (by saying that it can be "cured") is to ignore not only a huge body of scientific fact, but also to do the same as in, in the latter case, where the Church chose to ignore or suppress or persecute the views (and scientific proofs) of anyone who looked objectively at the evidence.
Science has moved on from the attitude of "we don't like this, therefore it's wrong", it's just that some who hold to "faith" in defiance of facts are not able to do so.