Arhat Culapanthaka's display of psychic powers to a layman (DP Verse 25)
It was not a show for people, that's the first thing you have missed. Here is how it went and what you missed,

The function in doctor Jeewaka's house was attended by the monks of the temple and Ven. Arhat Culapanthaka was at the temple/monastery. As Ven.Arhat Culapanthaka was alone and there was work to be done multiple bodies were used to clean the temple,to sweep it and do some other petty tasks. This is when the messenger from Doc.Jeevaka's house came and saw this.



Sometimes when arahats feel that more harm can come to a society or a person by not revealing his true status the Arahat does some suitable task to prove him that. This was first done by Lord Buddha to tame the ego of "Jatila sages" who thought they are Arahat and Lord Buddha was not. It was done again to tame the ego of the "Shakya cast" who were is relatives of prince siddhartha. 

What we need to understand is that Arahat does not break "Vinaya (laws &amp; guidelines of Buddhism)" no matter what. And that has been clearly stated in Buddhism. So there is no point in Scrutinizing the "Seela" or the conviction of an Arahat because it is not up to petty beings like us. Like always it has happened it should happen by the hands of another Arahat.