The first thing any knowledgeable Bible teacher, scholar or historian will tell us is that the interpretation of any Scripture is predicated on context according to the period of time that it was written (let alone the fact that it was written under the rule of a male-dominated society). The interpretation of Scripture must also take into account the audience at the time the Scripture was written. Further, one cannot successfully select or pick and choose the Scripture that they want to use to hate, kill or destroy another human being, just because that's the way they want it to be. In fact, for someone to attempt to justifiably use Psalm 109:8-9 to kill the President of the United States and leave his children fatherless creates a boomerang effect, because Psalm 109:8-9 is about David praising God for protecting his people. Therefore, the haters are actually using a Scripture that is counterproductive to their desires.
The exegesis of the entirety of Psalm 109 continues to indicate an EPIC FAIL on the part of the right-wing haters. Psalm 109 is broken down into the following chapter contents:
Psalm 109, Chapters 1-10 reflect David praising God for protecting his people. Psalm 109, Chapters 11-20 reflect the causes to praise him (not just David's causes, but humanity, in general).
From Matthew Henry's Concise Commentary: Chapters 1-10
If we would praise God acceptably, we must praise him in sincerity, with our whole heart. When we give thanks for some one particular mercy, we should remember former mercies. Our joy must not be in the gift, so much as in the Giver. The triumphs of the Redeemer ought to be the triumphs of the redeemed. The almighty power of God is that which the strongest and stoutest of his enemies are no way able to stand before. We are sure that the judgment of God is according to truth, and that with him there is no unrighteousness. His people may, by faith, flee to him as their Refuge, and may depend on his power and promise for their safety, so that no real hurt shall be done to them. Those who know him to be a God of truth and faithfulness, will rejoice in his word of promise, and rest upon that. Those who know him to be an everlasting Father, will trust him with their souls as their main care, and trust in him at all times, even to the end; and by constant care seek to approve themselves to him in the whole course of their lives. Who is there that would not seek him, who never hath forsaken those that seek Him?
From Matthew Henry's Concise Commentary: Chapters 11-20
Those who believe that God is greatly to be praised, not only desire to praise him better themselves, but desire that others may join with them. There is a day coming, when it will appear that he has not forgotten the cry of the humble; neither the cry of their blood, or the cry of their prayers. We are never brought so low, so near to death, but God can raise us up. If he has saved us from spiritual and eternal death, we may thence hope, that in all our distresses he will be a very present help to us. The overruling providence of God frequently so orders it, that persecutors and oppressors are brought to ruin by the projects they formed to destroy the people of God. Drunkards kill themselves; prodigals beggar themselves; the contentious bring mischief upon themselves: thus men's sins may be read in their punishment, and it becomes plain to all, that the destruction of sinners is of themselves. All wickedness came originally with the wicked one from hell; and those who continue in sin, must go to that place of torment. The true state, both of nations and of individuals, may be correctly estimated by this one rule, whether in their doings they remember or forget God. David encourages the people of God to wait for his salvation, though it should be long deferred. God will make it appear that he never did forget them: it is not possible he should. Strange that man, dust in his and about him, should yet need some sharp affliction, some severe visitation from God, to bring him to the knowledge of himself, and make him feel who and what he is.
It appears to me that the peddlers of hate, and those who are aiding and abetting it, are actually spreading blessings over the President and his family. Just as the haters can be redeemed and praise God, so can the President of the United States of America. Isn't that something? In the eyes of God, Barack Hussein Obama has the same access, blessings, redemption and every other thing available to him that the wingnuts have. After all, aren't the wingers serving an equal opportunity God?
It also appears to me that if any of these so-called right-wing Christians would spend more time in Bible class, and less time at tea parties and other hate fests, they would not be so easily punked in everything that they attempt to do that is pure evil.