I guess that you have been to a Pentecostal church once or twice and now you can confidently comment on its theology and practice. I spent 12 years in the Pentecostal movement at quite a number of levels, partly in leadership, and my opinion is quite different. In fact, I can confidently say that you don't know what you are talking about, because if you did, you would quite easily know that those who are faking are totally in the minority, and the majority of Pentecostal Christians love the Lord, have a passion for serving and being used of God. Most of the pastors and leaders I have worked with effectively deal with falsehood and know that those in the "lunatic fringe" are those who need spiritual help in other areas of their lives, the same as those in any church, Pentecostal or Evangelical.
Something else that interests me is that the majority of Pentecostals I know do not criticise other churches, possibly because they believe in this thing called "The fruit of the Spirit", and they don't see "put downs" and "criticism" as being part of the list. It leads me to believe that those who are baptised in the Spirit the Pentecostal way see and experience the fruit of the Spirit in a much stronger way than those of other evangelical churches who seem not to worry about their criticisms not being gentle. kind, or even basically loving. Maybe in their zeal for ignoring 1 Corinthians 12 and 14, they have cut out 1 Corinthians 13 out of their Bibles as well.
So called believers who are unloving, not gentle, and unkind to other believers, even Pentecostal, are not being motivated by The Holy Spirit. Then, I wonder what spirit does motivate them? And are they filled with the Spirit at all, but are filled with some other spirit that allows harsh, unkind, and even hateful criticism of Pentecostal believers?
Bears thinking about.
So the real issue is not whether tongues is genuine or false, but are those who are unloving, unkind, and harshly critical of those who speak in tongues, actually genuine Christians at all. Maybe the critics of tongues are the false ones! Maybe their whole religious foundation is false.