It strikes me that there is a difference between pedantry and railing against the evolution of the language, with the objection to 'top priority' falling squarely into the latter category.
The OED confirms the transferred sense of 'priority', "an interest having a prior claim to consideration; often in pl. or preceded by a qualifying word, as first, high, top priority." Good enough for me.
If we were to reject every transferred sense in the language, 'palette' for 'selection of colours' and 'frosty' for 'lacking in warmth of feeling' would be just two entries on a very long list indeed.