Just tell him,
“Therefore I want you to understand that no one speaking by the Spirit of God ever says “Jesus be cursed!” and no one can say “Jesus is Lord” except by the Holy Spirit.” (1 Cor 12:3)
So speaking in tongues is not the only evidence that shows you have the Holy Spirit.
I can understand your situation. I am myself a part of the Charismatic Renewal in the Catholic Church. It is supervised by our local Bishop in our area.
I myself received the gift of tongues many years ago, but I have as yet not understood their interpretation, so I don’t pray frequently in toungues. Paul says that those who have the gift of tongues should pray that they may be able to interpret it (1 Cor 14:13).
That Charismatic guy must be proud of his gift of speaking in tongues. But point out to him that God gives different gifts to different people, as the scripture says,
“To one is given through the Spirit the utterance of wisdom, and to another the utterance of knowledge according to the same Spirit, to another faith by the same Spirit, to another gifts of healing by the one Spirit, to another the working of miracles, to another prophecy, to another the ability to distinguish between spirits, to another various kinds of tongues, to another the interpretation of tongues. All these are inspired by one and the same Spirit, who apportions to each one individually as he wills.” (1 Cor 12:8-11)
Different people have different gifts, as Paul says,
“Are all apostles? Are all prophets? Are all teachers? Do all work miracles? Do all possess gifts of healing? Do all speak with tongues? Do all interpret?” (1 Cor 12:29-30)
“What then, brethren? When you come together, each one has a hymn, a lesson, a revelation, a tongue, or an interpretation. Let all things be done for edification.” (1 Cor 14:26)