In this week's parsha, we are taught about the meisis, the sinner who tries to seduce another to commit idolatry. We are instructed to deal with the meisis more stringently than with other transgressors. For example, his guilty verdict may not be overturned and we may use entrapment to catch him in the act.
The pasuk (13:9) says concerning the meisis, "lo soveh lo." Rashi interprets soveh‚ as derived from the same root as ahavah, love. He writes that although we are taught "ve'ahavta le'reiacha kamocha," you shall give love to your neighbour as you do yourself, to this man or woman, that commandment does not apply.
The gemara (Sanhedrin 45a) discusses the place where those who were to be stoned met their ultimate doom. The first step was to push them off a two-story cliff. The gemara asks why the cliff was not simply 10 tefachim high (less than two stories). We are taught elsewhere (Bava Kamma 50b) that this depth is enough to cause death. But the gemara answers that this would result in a more painful death and the Torah says "ve'ahavta le'reiacha kamocha," therefore, we must provide him a more proper and “pleasant” death. However, according to Rashi here, ve'ahavta le'reiacha kamocha does not apply to a meisis. Why, then, do we not kill a meisis by pushing him off a ledge only 10 tefachim high?
I asked this of a friend of mine who happened to have been bothered by the same question. He told me a friend of his answered from the gemara on 43b which states that he who is to be stoned does viduy, confession, before receiving the death penalty. It seems that even the meisis does this as well. Therefore, after he has confessed his sins, he may now be included in the mitzvah of ve'ahavta le'reiacha kamocha and is deserving of a more proper death. Rashi in the parsha is referring to the processes carried out beforehand and thus, he is still excluded from the mitzvah of ve'ahavta le'reiacha kamocha. (It should be mentioned, however, as one reader pointed out, that the Minchas Chinuch writes that teshuvah is not effective regarding a meisis; if so viduy also won't be operative and this is not a valid answer.)
Perhaps another answer may be offered. Rambam (Hilchos Avodas Kochavim 5:4), in explaining the practical prohibitions connected with this pasuk, writes, "It is forbidden for the seducer's target to show love towards the seducer." It appears from Rambam's careful wording that the prohibitions discussed in this pasuk are directed specifically at the seducer's target and not the general public. The beis din, who are responsible for carrying out and overseeing the execution, are thus never absolved of their obligation of ve'ahavta le'reiacha kamocha toward the meisis.