Psalm 2:12 and counter missionaries

Essentially, I agree with the counter missionary position that many Christian bible intentionally mistranslate Psalm 2:12 to say "kiss the son" because the KJV and Martin Luther did.  I was in a counter missionary room where this issue was brought up, then we went on to discuss Ibn Ezra, the rabbi that was the source of what would cause Luther and the KJV to say "Kiss the Son."  Rashi was being brought up on the matter, and his rendering of Psalm 2:12, which is not what Ibn Ezra said.  Anyway, traditional Catholic bible for Psalm 2:12 say something along the lines of "cherish discipline." The issue I had with the counter missionaries they made the claim the Psalms never use Aramaic.  This claim is disputable.

Psalm 55:22 reads:

Smooth were the buttery words of his mouth but his heart was set on war; his words were softer than oil, but they are curses [פְתִחוֹת].--Psalms 55:22

RASHI comments:

but they are curses Heb. פתחות. Menachem (p. 147) interpreted it as an expression of swords, as (Micah 5:5): “and the land of Nimrod with its swords (בפתחיה),” with the edges of the sword. I say, however, that it is an expression of curse in Aramaic, as the Talmud (R.H. 31b) states: Amemar wrote a pethicha on her, which is a warrant decreeing excommunication.

The point of this is that it seems RASHI insists that the word פְתִחוֹת f'tichot is Aramaic. This is interesting since virtually every Christian translation of the Psalm has the word "sword." Regardless, the point stands, one of the most respected Jewish exegetes of the Hebrew Bible seems to insist Psalm 55:22 uses an Aramaic word, contrary to the claim made by some counterMissionaries that the Tanakh never uses Aramaic, claim it was only used at a LATER time with the interaction of the Babylonians.  It is interesting that not only the later books of the Hebrew bible uses Aramaic like Daniel, Ezra, etc, but also Genesis uses Aramaic in a verse!