Commentary for Avodah Zarah 140:7

The baraita refers to a case where there is an inner and outer courtyard, the inner one belonging to a haver and the outer one belonging to the am ha’aretz. Although the am ha’aretz could stretch out his hand and touch the haver’s belongings, we do not have to assume that he did so. The haver’s stuff remains pure. This seems to contradict Rav.
Rav answers that this refers to a case where the am ha’aretz will fear getting caught—looking like a thief. Thus he will be deterred from touching the haver’s pure things. But if he has no such fear, the pure things would have to be considered defiled.