I agree. It seems to me Hale would want to believe this statement, even used to believe it. Now, after his experience in Salem, he can no longer believe this is true. He tried it and he failed. It's just that simple. He has become disillusioned enough to beg fellow believers to lie in order to save their lives, knowing both that they do not deserve to die and that lying is a certain condemnation to hell (according to their faith).
Your speech, I think, should reflect the facts but also convey this emotion of bitterness and hopelessness for this loss of faith. The speech should be a tragic reworking of the earnest hope Hale once had that it was the Devil who was at work in Salem:
"Have no fear now--we shall find him out if he has come among us, and I mean to crush him utterly if he has shown his face!" (Act I p. 39)
Sadly, he now knows it was the work of humans who created this mess. That sadness, I think, is Hale's overwhelming response to the events in Salem.
This one is going to be a challenge because Hale, himself, is a challenge to assess. I think that the starting point here is whether or not you personally endorse Hale as an overall character who is trapped by the demanding political and social challenges of Salem or if you feel Hale was part of the problem in Salem. This will be the fundamental decision that you have to make before writing your speech. If you choose to empathize with Hale, you probably would point to his understanding that Proctor understood a higher level of truth than was being advocated in Salem at the time. In regretting his affair and accepting punishment for this sin and not the politicized aspect of witchcraft, you would speak of his high caliber of character. You would also stress the how difficult it was to stop the "bloodletting" of false accusations and institutional realities, as you would pit yourself as one of the few voices of reason in a setting devoid of it. Essentially, your speech would admit weakness but would stress that you understood "truth" better than others in the position of power. If you went the opposite, I think you speak from a position of guilt. Essentially, you ask the question of what good was understanding the truth, if one is powerless to act upon it? Hale understood and comprehended the truth being practiced, yet he succumbed to political reality, a sick sense of pragmatism and vendetta driving justice and policy. I think it would be strange to have Hale condemn himself, so I think striking a tone of guilt would be the best approach in suggesting that his efforts were futile, resulting in the death of innocent people. This condemnation would be something from which there is no escape.