We need not necessarily quote from Scriptures all the time. As long as our practice is not in variance with the dharma, we can always go by it and explain it in general terms. If a genuine practitioner of dharma says something it carries full conviction.
Dharma is of two types, sAmanya dharma and viSesha dharma . In order to properly understand the intricacies of dharma for practical appliication in a specific situation, we may have to refer to the Scriptures as they constitute the root of dharma.
One word of caution. While rationalizing one should not contravene the Scriptures.
Rationalization manifests as a poem while Scriptures constitute the prosody.