The truth is that they harm Islaam and further turn people away from it.
The Muslims reached the point where they almost want to cover their faces in order to avoid being attributed to this terrifying group. Islaam is free from it. Even after Jihaad was ordained, the companions of the Prophet never used to go to non-Muslim societies and kill them, never! There is no Jihaad except under the banner of a ruler who has the ability to carry it out.
As for terrorism, by Allaah it is a deficiency on the part of the Muslims, I swear by Allaah, we never see its benefits, rather it is the opposite, it distorts the reputation of Islaam. But if were to act with wisdom, fear Allaah within our own selves firstly and then try to rectify other people’s affairs with legislated methods, the results would be positive.
Al ‘Alaamah Muhammad ibn Saaleh al ‘Uthaymeen
العلامة محمد بن صالح العثيمين –رحمه الله-
Fataawa al A-imah: p.55
فتاوى الائمة: ص:55
Terrorism only causes Muslims living in their own countries to be killed as you are now witnessing. This is not from the affairs of Da’wah, nor is it from the affairs of Jihaad. Likewise bombings and causing destruction, this only draws great evil upon the Muslims as is now happening…
Al ‘Alaamah Saaleh ibn Fawzaan Al Fawzaan
العلامة صالح بن فوزان الفوزان
Fataawa al A-imah: p.65
فتاوى الائمة: ص:65
Question: Is it permissible to hijack planes, blow up buildings and carry out revolts [against the government]? Is this considered to be from the essence of Islaam that one loves to act upon? Benefit us, may Allaah reward you.
Answer: These affairs are from the destruction that Islaam prohibits, and it draws a lot of evil upon the Muslims because the non-Muslims take this as grounds to attack the Muslims and annihilate them. It is these actions that non-Muslims have used as justification to dispraise Islaam as being a religion of terrorism, they say this because of such activities.
Islaam prohibits Bombings, destruction and hijacking planes because it causes harm to the Muslims before it does to other than them, and because it is a form of harm that does not contain any benefit.