Luke 23:49 says "And all his acquaintances and the women who had followed him from Galilee stood at a distance watching these things."
So I suppose anyone who ever stood at a distance and watched someone far away is the messiah? Or is it the person far away (who is being watched) who this list maker is claiming is the messiah?
Let us look at the first line. "A song with musical accompaniment of the sons of Korah, for the conductor, about the sick and afflicted one, a maskil of Heman Ha'ezrahi (the Ezrahite)." Rashi (the great commentator) tells us that the sons of Korah composed this prayer with the intention that it be sung by Heman Ha'ezrahi. Heman is identified in the Book of Divrei Hayamim I / II Chronicles 2:6 as a descendant of Judah's son Zerah, thus accounting for his name "Ha'ezrahi" ("Ezrahi" from זֶֽרַח (Zeraḥ), the younger of Judah's twin sons by Tamar—from whom both Heiman and Eitan were descended (see Divrei Hayamim Alef / 1 Chronicles 2.6). הָאֶזְרָחִי (ha'ezraḥi) is cognate with הַזַּרְחִי (hazarḥi, "the Zeraḥite") which occurs in B'midbar / Numbers 26:13 & 26:20, and again twice in Y'hoshua / Joshua 7:17.). He is also listed in the Book of M'lachim Alef / 1 Kings 5:11 "And he was wiser than all men, than Ethan the Ezrahite, and Heman, and Chalcol, and Darda, the sons of Mahol, and his fame was in all the nations round about."
It is important to understand the context of the psalm -- in this case we are being told it was either sung by Herman or composed by him -- to be sung in the Temple as a prayer. It was not prophetic and it had nothing at all to do with people standing "afar off" and watching anything.
What of the claimed line?
What of verse 8? This is verse 9 in the T'nach (because most Christian versions either eliminate the first line, or do not number it) -- but it has to be read in the context of the psalm itself which is a plea for G-d's help in a time of dire need. The author speaks of being close to death, and that he has been abandoned by his friends (one can see how this might be attractive to a missionary -- but Jesus was not the only person to ever feel this way).
In verses 4-19, the subject complains that he is being treated as though he were dead -- saying that people already speak of him as deceased. He describes the "depths" and "darkness" in which he lives, practically on the brink of the grave. He laments the fact that his former supporters now look upon him with contempt and keep their distance from him, leaving him to wallow and wither in isolation.
Ibn Ezra thought the psalm was speaking of a person who lay dying from a potentially contagious illness, thus even his closest friends refuse to visit him because of their fear of contracting the illness. Other sages see it is the Jewish nation -- often isolated and despised in exile. . .
One can see why the psalm might be tempting to a missionary -- but it hardly applies to only Jesus. It is a far more universal experience, and thus cannot be a messianic prophecy.