After quite a bit of time away from the blog, I'm just going to toss out a couple of ideas on this topic, as promised...
First, before we can respond, we need to be made aware of these invalid understandings (in ourselves as wel as in others). This is why it's so important to read Scripture in community - in community with our brothers and sisters in Christ from around the world and throughout history as well as, most importantly, in community with the Holy Spirit who dwells within us.
Second, check out this article on perspective and preference:
Third, be humble and gentle. Nine times out of ten the invalid things our friends believe are not core issues, not worth quarreling about, and not as clear as we think.
Lastly, I've found it helpful when I get frustrated by talking about these ideas and feel that truth is escaping me to know that:
"Biblical truth, the truth in which the people of God are called to live...is concrete, historcal truth. It does not exist in a world of pure ideas but rather is closely bound with bread and wine, with justice and peace, with a coming Reign of God-a Reign not over pure ideas or over disembodied souls but over a new society and a renewed history" (Gonzalez, Manana, p. 50).