Blasphemy's CONCEPTION is indeed in the heart, but it's birth takes place in the mouth or tongue, or actions. So the question remains.
Are some of the babbling, NON-LANGUAGE tongue speakers, slain in the spirit, riotous laughing, rolling on the floor, exaggerated tic and head shaking, people faking, NONE of which is found in Scripture, mocking the Lord, or blaspheming the Holy Spirit?
Most probably aren't blaspheming the Holy spirit, or even knowingly mocking the Lord. Just desperate to have some type of what THEY think is a real EXPERIENCE to ease their lack of faith that the sufficiency of the inspired, Living Word is enough.
When the EXPERIENCE, which I absolutely believe DOES happen, is the goal, instead of seeking the Lord, AND HIS WILL, through His Word with prayer, and letting HIM provide the assurance of His Presence, then by necessity it has to be MANufactured. And I think that's what goes on in these places.
Almost like when Abraham's faith wavered, and HE tried to help God's plan along by taking Hagar with the intent of fulfilling God's promises, similarly, many of the Charismatics do not have the patience, or faith to wait on the Lord.
Hard truths they don't like, but maybe some will consider.