The part of the sentence "be regarded as proof" is correct and usable in written English.
You can use the phrase to indicate that something is considered to be convincing evidence for something else. For example: "The results of the study were regarded as proof that the new vaccine is effective."
If some of its manifestations appeared contradictory, that could be regarded as proof of its vitality.
In Hindu codes a wife may be required to pass through fire to prove her fidelity to a jealous husband; traces of burning would be regarded as proof of guilt.
Thus, the results of the model refitting cannot be regarded as proof for our hypothesis about the causality between system acceptance and learning.
Nevertheless, this observation cannot be regarded as proof of a possible treatment effect.
Therefore, the detection of anti-A or anti-B alloantibodies cannot be regarded as proof of a possible alloimmunization after AB0 incompatible transplantation.
This increased risk is, of course, a predictable side effect of a procoagulant drug, and can actually be regarded as proof of its physiologic effect.
We and others argued that previous studies with SDD in intensive care and cancer patients can be regarded as proof-of-principle for the efficacy to prevent infection by topical decolonization or at least suppression of potentially pathogenic enteric bacteria.
Now, more than ever, the statements are being regarded as proof that the media is in cahoots with the Trump campaign.
As the flames shot up, an apparition swooped down to rescue her, and the blood-red markings on a stone that sits beneath that same locust is regarded as proof of this event.
Bold ideas that could mobilize his conservative Republican base were prized over efforts to convince independent voters in the center; sharp divisions over the administration's policies were regarded as proof of Mr. Bush's decisiveness and willingness to challenge conventional thinking.
The main character in the book, a lawyer, earned the nickname Pudd'nhead in part because he spent so much time collecting "finger-marks" — which was regarded as proof of his foolishness until he astounded his fellow-citizens by using the marks to solve a murder.
