I'm stunned that John 15.26 is really considered to be so insufficient by Roman Catholicism when addressing this issue. The very Son from whom the Spirit is supposed to proceed says the Spirit proceeds from the Father, and that's not good enough? They can take him at face value re: Matthew 26.26-28, but not here?
Oh gosh like I said again... Other passages affirm it as St Augustine pointed out. But ignore western theology and saints abs the Latin language and pronounce the Greek only.
You claim that other passages affirm Filioque's orthodoxy, but you haven't demonstrated that conclusively, you've merely asserted it. Meanwhile, we have a quote from Christ himself directly relevant to the issue. If Western theology and saints and the Latin language have no need for Christ, just say so. But don't claim Christ and ignore his very pertinent statement.
Procedit accommodates filioque because it concerns motion, not origin.
You don't get it.
If procedit concerns motion and not origin, how is it a translation of ἐκπορευόμενον, which does concern origin? Either it is
a) a bad translation (which is itself problematic, and there are other examples in Western tradition of bad translations causing havoc), or
b) the Latins decided that they didn't want to discuss the origin of the Holy Spirit when professing the Creed, and so they decided to change the topic to "motion", redefining terms and meanings as they pleased. You can't do that unilaterally, you can't agree to use certain words and then redefine them later because you feel like it might be nice or useful.