Unfortunately, the Church herself has demonstrated (from outside the clergy) some evidence of Gnosticism to the exterior witnesses. The doctrine of the Trinity, for instance. Any of the great prounouncements. The selection of Scripture - and the particular version of each book of Scripture - and so on.
There is not a good explanation for it to the laity. A bunch of bishops disappear for a fortnight, and come out with the results of the latest Council. I'm not suggesting that they do other than what they do, but they do provide some examples to the heretic and the separated brethren. I understand that the separated brethren do not have the qualifications or the authorization that the Church does, but think of a 6 year old kid, watching his father go to the ATM and pull money out. That kid would give anything to be able to do the same, not realizing the whole business behind being able to pull money out of the ARM.
You’re right. That’s a good point.