An academic discussion: As per Islamic belief there are three types of creation; namely, NOORI, NARI and KHAKI. Noori are angels, Nari are Jin and Khaki are Humans. Therefore, as far as Muslims are concerned Jins are present and reality. In western countries also subject of ghost is not neglected; quantum of efforts are being diverted to study effected properties and other related phenomenons. Similar concepts are present in Hinduism as well. So it can be concluded that there exists another creature which is not visible to human eye.
Now coming to their capabilities to harm humans. As per Islamic point of view Humans are "Ashraf ul Makhloqat" Superior to all Creations (words to that effect). It is due to this reason, despite being physically weaker then many creations, humans have been able to tame and control those. E.g. It learnt flying from birds and developed the capability of going beyond envelop of birds' operation. Therefore, any supernatural creation cannot be superior to humans, it can be controlled by humans. Yes there exist a chance that mishandling them may lead to human injury or harm. Just like in the case of any wild animal.
Talking about Peer who claim to be experts in controlling Jin. Most of them are fake. However, people with special powers do exist. Litmus test is that they will never put their capability for sale or advertise their powers. Their objective will be to help people rather then to fleece. A true capable person will never demand any money or put extra ordinary demands. There are few who ask to do some charity, but do not take this amount themselves.
I read a post with regards to Sura-e-Jin. This is an individuals experience. I have heard that if you recite Sur-e-Jin aloud, past midnight and you make a mistake in recitation, Jins do the correction. It is a concept I heard, which I have neither experienced nor got an authentication from anywhere. I shared it because of the subject under discussion. But, yes I do have experience with this invisible creature, so far not very unpleasant, yet you need to learn how to co-exist.