First, it does NOT mention the idea or the word torture.
It was not a teaching but a matter of discipline. Teachings are matters of faith or morals addressed to ALL Christians, not just those of a particular time or place.
If a doctrine is not binding on all Christians for all times, it cannot be a teaching.
Ad Exstirpanda no where mentions the word torture or implies torture. " When those adjudged guilty of heresy have been given up to the civil power by the bishop or his representative, or the Inquisition, the podest or chief magistrate of the city shall take them at once, and shall, within five days at the most, execute the laws made against them."
First, torture was used by some to elicit an admission of heresy. The Popes never, ever taught that torture was permitted under any circumstances in these cases. Torture was an idea that was a hold over from pagan goverments and these goverments were the ones who pushed this idea in order to elicit a testamony of guilt. The Church NEVER taught this was permissible.
The civil powers who considered heretics to be traitors, not just heretics, in which case the civil powers
had the right to prosecute them as traitors. In this case the civil goverments had the right to prosecute them as they saw fit, even the death penalty for example, as they did with St. Joan of Arc, even though she was convicted unjustly with the help of some bad bishops.
Sometimes the state had lesser punishments. But it was the state govements determing the laws made against them and the punishments and NOT the Popes. Do the Popes tell our goverment how to punish traitors? Of course not. Would our goverment listen anyway? Of course not. The Popes originally wanted certain types of heretics to be expelled from the country. And those were only the onces that advocated suicide or who advocated husbands to abandon their wives and children, so they could live in fornication with younger women. In other words, the Popes only advocated those heretics who were gravely harming society to be expelled. But, when the goverments prosecuted these types of heretics, they fought back, started wars, etc. The goverments then considered them to be traitors and the enemy, and thus used harsh measurers against them.
The Popes never advocated the harsh measures, but they have always allowed the state to use punishments the death penalty, for serious crimes, as they do today, but only as the last resort. The Popes actually took in those who were fleeing the prosecution by the state.
So when we read.
" 1. In the Papal Bull, Ad Exstirpanda, it was declared that it was allowed under certain circumstances to use torture."
These are interpretations by anti-Catholics who have no desire to seek the truth. No where does the Church advocate or permit torture and never did the Church advocate or permit torture. The Church allows the state to proscute prisoners or the enemy, but she has never ever taught that goverments should use torture.