Parshas Vayera describes Avraham Avinu's persistent, impassioned plea on behalf of the inhabitants of S'dom. "The people of S'dom were exceedingly evil and sinful to Hashem" (Braishis 13:13), and, accordingly, Avraham Avinu hated them as deeply and intensely as possible. Nonetheless, Avraham Avinu was concerned with their welfare, as a father concerns himself with the welfare of a wayward son. Hence his plea to Hakadosh Baruch Hu to spare them. This trait of yashrus, notes the Netziv in his introduction to Sefer Braishis, was the hallmark of the avos.
In a similar vein, the Gemara (Berachos 10a) recounts that some evil people were making Rebbe Meir's life miserable. He prayed for their demise. His wife, Bruriah, remonstrated that the pasuk says "Yitamu chato'im min ha'aretz ureshaim od einam" - may sin be eradicated and thus there will be no more evildoers (because all will have repented). Rebbe Meir accepts his wife's rebuke, prays that the sinners repent and that is exactly what happens.
Recently, there have been reports in the press of individuals wishing for the death of Prime Minister Ariel Sharon. By no means am I assuming the veracity of such reports. (Moreover, even these reports attribute such malevolent wishes to an isolated few.) Thus I am commenting on the issue, not on any specific persons or alleged remarks. Harboring such violent wishes is absolutely antithetical to Torah. Avraham Avinu had no sympathy for the perversions practiced by the people of S'dom. He abhorred the torture to which the young girl who had extended hospitality to a guest was subjected. Nonetheless, Avraham Avinu attempted to intercede to save the people of S'dom. He wished for their rehabilitation, not their destruction.
In a similar vein, one may be opposed to Sharon's disengagement plan. (Needless to say, I am not equating Prime Minister Sharon with the people of S'dom. The issue is how and for what do we pray when we oppose the beliefs, practices or policies of others.) In the realm of prayer, we may certainly pray that this plan be foiled. We need not tell Hakadosh Baruch Hu how to foil the plan. He does not need our advice on political strategy, and He does not lack the means to bring about the desired result! And if we are to specify a scenario, we should pray that Sharon reverse his position, and not, rachmana litslan, that he die.