Selective trust without reasoned grounds is capricious and not genuine. [causal]
If "trust" is selectively directed at only certain other people but not based on grounds for selecting which others, then it must be capricious—unrelated to its objects and not a consistent expression of character. Such "trust"—which should be characterized as acting as though one trusts—seems neither sensible nor meritorious.
DEFINE: Distinguishes genuine trust from 'acting as though one trusts' — a conceptual clarification of what counts as real trust.
Russell Hardin, Trust and Trustworthiness, loc. 945