It’s not that Judaism and Islam are somehow more acceptable than Protestantism. It’s more that there are concentric circles of similarity that we can rely on when we dialogue with others.
- Fellow Latin Catholics
- Eastern Catholics (fully Catholic, but with some different practices — they would presumably say the same about Latins)
- Orthodox Christians (true churches, ancient and sacramental, but not in communion with us at present)
- Protestant Christians (followers of Christ, united by baptism, at varying distances in terms of belief and practice)
- Jews (worshippers of the God of Abraham, our spiritual forebears; we include their Scriptures in our own)
- Muslims (worshippers of the God of Abraham, though a later offshoot that claims to be a “correction” of Judaism and Christianity — but we have many honored figures and stories in common)
- Hindus, Buddhists, neopagans, and others that are not historically connected to us at all
When Church documents speak favorably of Islam, or any other religion, they are doing so in this context — that they have similarities, pieces of the truth if not the whole picture. Note that the Church does not anywhere claim that Islam is true in all particulars, or worshipping God acceptably, or actually revealed by God, or salvific in and of itself (though individual Muslims, like others, may be saved if they are acting in ignorance of the full truth and are sincerely trying to do God’s will as they know it). Only that, historically speaking, it is “aiming” for the true God, even if it has wrong ideas about Him. In this it is similar to Judaism (which, despite its very close ties to us, was treated
very poorly in Christian rhetoric of past ages) and different from other, more distant non-Christian religions.
The fact that, these days, we tend to emphasize similarities and the pieces of truth that other belief systems do have, rather than focusing on differences and errors, is indeed a change from past practice — but it seems to be a Spirit-led and welcome one. Heck, within Christianity itself, we’ve started to heal a schism that goes back to the early ecumenical councils, by ceasing to call each other heretics long enough to discuss what each side actually believes; and what do you know, after 1500 years or so we’ve figured out that both sides were trying to defend the same truth, but each thought the other’s choice of language was inadequate to do so! If only we had conducted such dialogue far sooner!