Again, technically speaking, this is a prayer where the pray-er is asking St. Michael's help to pray with and protect them through the power of God, which Scriptural and acceptable. It is decidedly not a prayer to the Archangel in "competition" with God. I find no problem with it, and can't figure out a problem with it Scripturally.
Holy Michael, the Archangel, defend us in battle. Be our protection against the wickedness and snares of the devil. May God rebuke him, we humbly pray; and do you, O Prince of the heavenly host, by the power of God cast into hell Satan and all evil spirits who wander through the world seeking the ruin of souls.
Exactly. You said Catholics don't pray "to" saints and angels. Here you go. Catholics in this prayer are praying TO Michael not WITH him...Michael is being addressed, not God. Nice way to split hairs and all, but God isn't the only one with the power if Michael is doing some of the protecting. Don't look for Michael to defend you in your spiritual battles. Why don't you look to Christ instead? He tells you to come to Him, not Michael, in the New Testament.
You defended the accusations of "worshiping" Mary and the saints very well. However I think you're wasting your time. People see what they WANT to see.
Some Protestants (not all) will continuously repeat the worship mantra no matter how many times we tell them we worship only God but honour the saints. How they can read our minds telling us we're wrong, I'll never know.