The gemara says that when the judges get a feeling that the litigant is unscrupulous he should take precautions to do drishos v'chakiros and thoroughly investigate the witnesses. But if he doesn't have any reason to suspect the litigants, there are no drishos v'chakiros necessary by dinei ma'monos. Tosafos asks that we find in shavuos 30b that the beis din should abstain from judging when the litigant isn't a decent person based on מדבר שקר תרחק. Tosafos answers that the gemara in shavuos is speaking when the beis din knows with certainty that he is crooked, but here we are speaking about they merely suspect a din me'rumah. The Rosh offers another approach to answer Tosafos' question. The gemara in shavuos is speaking when the claimant is suspected of being unscrupulous, therefore it is best for beis din to abstain from judging the case at all, thereby preventing him from unjustly taking money from the defendant. But our gemara is speaking where the defendant is unscrupulous, so the beis din is required to get involved to protect the claimant, but they have to be careful to cross examine the witnesses properly.
Rashi doesn't seem to fit with either approach. Rashi says that we are speaking here when the beis din knows that the claimant is a thief (ra'mai) or they understand from his claim that he is deceitful. Rashi can't hold of Tosafos answer because we even speaking about a case where they recognize him as a known deceitful person. Rashi also can't hold of the Rosh's approach because he says that we are speaking when the claimant is known to be deceitful, not the defendant.
To be mekayem שלשים יום קודם לחג שואלין ודורשין בענינו של חג, the maharatz chiyus points out that we find in the gemara that R. Akiva was from b'nei berak, and R. eliezer from Lod. They were too far from one another to travel on yom tov. Being that R. Eliezer had a well documented opinion (succah 27b) that one may not leave their home for yom tov (since they are required to be mi'samei'ach their family), how can the Haggadah tell us that R. Eliezer spent Pesach night in B'nei Berak with R. Akiva telling the story of yetzias mitzrayim?
Perhaps the Ba'al Hagaddah is trying to prove that the mitzvah of sippur yetzias mitzrayim is not all or nothing, but can be fulfilled at different levels. One who is more capable of darshening in detail and depth is obligated to do so, whereas one who is not capable can be yotzei with a more minimal discussion. This is clear in the Rambam when he discusses the mitzvah of sippur. R. Eliezer realized that in Lod he couldn't fulfill the mitzvah of sippur at the level that he was required to and therefore was willing to forfeit staying at home (and lose out on that mitzvah) in order to properly fulfill the mitzvah of sippur yetzias mitzrayim.