[Always Right]

In any event, Catholics consider Sacred Tradition to be the work of the Holy Spirit, and therefore on a par with Scripture, yet it is rejected across the board within Protestantism as being "extra-Biblical."

I don't have much issue with stuff that is 'extra-Biblical', it is only when it seems to conflict with the Bible when I have problems with it.

[magisterium]

seems

There's the problem! While it "seems" to conflict with what you think the Bible says, it "seems" to harmonize perfectly with the Bible in the minds of any number of Catholics. Who decides who is right? In Protestantism, at bottom, it is the individual believer. But, as already discussed, their mileage may - and does! - vary considerably. They have no equivalent of the Magisterium to make such determinations. Indeed, that role as final arbiter is possibly the best common-sense support of Catholic Scriptural argument in favor of the role of the Magisterium. Its absence leads, quickly and inevitably, to doctrinal chaos.