When you tell someone that they don't have the Holy Spirit, when you have indeed tested the Spirit, you know the Spirit that they operate in, and God has revealed to you who they are, that is not blaspheming the Holy Spirit.
Because the Lord tells us that there is a sin that is not forgivable, and that is blaspheming. But what false prophets do, they twist scripture.
So stop allowing these false prophets to manipulate you and scare you into thinking that you have blasphemed the Holy Spirit. Because you see the Spirit that they operate in, you have exposed it, and you are calling it out for what it is.
Don't let another false prophet scare you into thinking, if you expose them, that you are blaspheming the Holy Spirit. That is manipulation and witchcraft that they use to try to shut the mouth of God's people.