An open source project or any other volunteer run project is dependent on people wanting to give their time and effort in the hope that the project will produce something they want. One of the major causes of failure is people who are disruptive, not necessarily deliberately, but who don't fit in with what needs to be done.
Effectively a disruptive person is poisonous because they can cause a project to sicken and die by causing more productive people to misdirect their effort or drop out. Perhaps poisonous is not a tactful description but it is evocative.