You have established your argument on several points, including:
1) that the effect of blasphemy on the believer counts as harm
2) that such harm is settled in courts and results in removal of protection from speech
I offer a third point which demonstrates Voltaire and Dawkins must, according to your standard, lose protection of their speech:
3) to deny God’s existence is necessarily blasphemy if God in fact exists (and to the believer, he does).
But incurring harm alone is not the test. Absence of reason must accompany the harm to constitute a tort.