I believe those accusations were the works of the devil.
Because he couldn't find faults with the teachings and publications of the TFP, he spreaded ridiculous calumnies about them which were not based on evidence.
Our Lord said you can know something by its fruits. The fruits are always correlated with the sanctity of a soul. The TFP actually has done a lot of good for the Church - for examples: Annual Public Rosary Rally, Promotion of the Rosary, Promotion of devotion to Our Lady, etc.