Read up on European responses to the military jurisprudence of their Muslim adversaries, sometimes. Note how they admire their moral character, and often even decry their own neighbors in comparison.
This is a bit more complex than you think. The praise of adversaries, especially in vitaes, does also serve to raise the glory of those that defeat them. To portray something foreign as noble in certain regards is also "posh". A perfect status quo in written down is also vastly different from what people actually accept as good or okay. Take today time: In theory for any citizen of the western industrial countries it would be good to donate for the poor over in afrika, pay higher taxes for the best healthcare of all people etc. But how many actually do or support that? Not so many. Would we go so far and call their every day live bad? No. Why? Because good/bad is always up to perspective.
Also, the Templars literally went against their own vows throughout their careers. That is evil by their own worldview.
They look at the world and see a Frank Miller grimdark hellscape where all "good" is hypocritical lies meant to keep the weak from challenging the strong, because that's all they know.
So from their perspective they do the good thing because it is their way of live and right to do so.
Do you think they go to bed and reflect: "Oh boy, today I was evil."
I doubt that this would account for the entirety of the race.
Send slaves to fight against professional warriors?
Put people into prison?
There can always be made an argument to what would be the "good" choice yet we take things away from them that could be considered evil.
We do this for a reason.
Take away fredom "evil" to protect others "good".
Kill people "evil" to protect others "good".
It always boils down to how we put things into perspective into the agreed upon current norm. And yes, it was a different time pretty much applies to this. Even morality was not invented in modern times, it still was very different. Morality on its own just means that you have a moral, not what kind of rules are part of that morality.
You may very well think slaughtering an entire town to capture it in a blood bath may be a bit itchy, but then capturing it for the only true faith and getting redemption and forgiveness in the end makes it okay.
That was one of the MAJOR drives of the crusades. The absolute and unconditional absolution that was promised. You may do the most horrible things but in the end: Absolution. You are good and pure again, say hello to the paradise. Keep in mind, as you said, the first crusade was an important tool to keep the troublesome nobility in check and stop them from feuding as much as they did at that time. Only with the first crusade became the Miles christianus one of the most identity granting ideals of nobility and knighthood. The dominant institution for morality integrated the fighting class into its rules more tightly and while that prevented some violence amongst those with the same faith, it allowed for the most gruesome cruelty against those that were not.
Thing a few years back and slaughtering Chinese in the thousands was pretty much acceptable for European countries. Not to speak of other colonial territories. Sure, they may have always been a few voices against it, but the dominant idea was: Imperalism is friggin great, especially the wealth it brings. If a few natives die, who cares.