Luke and the Samaritan

this is an interesting parable to me. He uses it to make the Jewish priestly classes out to be the enemy (which they were in the story of Jesus and thus the need for a comparison of this nature) or the selfish uncaring ones because they do not want to jeopardize their status of ritual purity. my curiosity about this parable is (and Luke would be well aware of the following fact) why, when Mikvahs were/are a dime a dozen in Israel (I've seen the archaeological remains 1st hand, as well knowing what defines a Mikvah one would only need find a natural body of water to have one) would Luke make his point around this? that is, these two Jewish men would have easily been able to cure their ritual impurity so its hard to believe that they passed up this man based on that fact. I would be more comfortable with these two Jewish men being selfish and having racism towards the man in the ditch who was not Jewish(which they would have) then them being against touching a supposed dead body. how do i know he's not Jewish, cause if he was they wouldn't have ignored him - believe it or not but the Body is incredibly important in Judaism as is the mistreatment and neglect of a body and this would never have occurred if the man was a Jew.In Judaism Chevrah Kadisha is considered a BIG Mitzvah and it goes against the Jewish beliefs of Tzedakah and performing Mitzvot to say these men didn't want to care for a dead body. But it is incredibly believable to me that these men chose not to deal with a non-Jew because there was a very pervasive desire in Ancient Israel to segregate from the non-Jew. Now these 2 men would not be handling the care taking of a non-Jew's body either but that simply reinforces the argument for them avoiding the man because of his ethnicity and not because he may be dead.