What is the correct methodology toward the da'wah groups?

Question:
Many young people invite me to join them in calling to Allah, and they are from a group called "Jama'at al-Tabligh." What is your opinion on this? Should I join them or not?

Answer:
There are many groups, various groups, so there is no harm in joining them in good and calling to it, not in everything. If someone invites you to good, you join in the good: Jama'at al-Tabligh, or Ansar al-Sunnah, or the Muslim Brotherhood, or a Muslim group in another country, or a da'wah group in another country, or something similar in name, or the Islamic Center, or the Islamic Union, or the Union of Muslims, whatever name they give it. If you are invited to that, participate in the good, and do not participate in evil. Respond to their request in what concerns the pure Shari'ah, and deny to them what they have contradicted of the pure Shari'ah. Make yourself a means of good and a caller to good, urging them to adhere to the command of Allah and warning them against division and disagreement. Do not be with them absolutely, nor against them absolutely, but be with them in good, and against them in what they have erred in, until they are guided and adhere to the truth.