visit here THE SCARY GENTILE
[26a middle] Gemarah: If a gentile came with Jewish tax collectors to search houses, the collectors are trusted [to testify about a house’s contents being contaminated or not] to say that they did not even enter the house, but not to testify about if they actually did not touch anything within it [because the overseeing gentile probably made them rummage through items which would have made the items Tamei (impure)].
R’ Yochanan and R’ Elazar: The presence of a gentile influences their trustworthiness because: 1) The gentile creates fear in the collectors to thoroughly search the house to get their taxes due (and they risk punishment from the overseer for their incompetence) or 2) The collectors fear that this gentile will report them to the king if they do not do a thorough job.
http://ouritblog.com/author/neerajguptablog/page/11/ T’s lesson: We must always be wary of non-Jewish power and influence. If even one gentile had influence on tax collectors (and the consequent laws we made regarding impurity), how much more so must we be careful while living in Galus (exile) under the power and influence of so many gentiles, with much power! We should always be careful and safeguard ourselves to avoid problems in the world which we live.