In a world similar to ours, mankind has invented time traveling technology since hundreds of years ago. Initially, it was very costly and only conducted for scientific purposes but nowadays it's became a mundane technology that's limited by a particularly scarce mineral for its fuel.
Time travel could only be done to the past because the future is yet to be determined. It's became public knowledge that any changes to the past would make a parallel timeline which is completely independent of the original one. Therefore, people could do time travel and take advantage of--or even abuse--it (given they could afford the fuel).
Time travel is forbidden by the World Government unless it's deemed necessary. There's no special force to enforce the rule but the police does regular checking against possibility of time travel abuse.
A growing and sufficiently-funded religious sect deemed the parallel timeline as an affront to the Creation.Therefore, they plan to destroy every one of those timelines.
The question is how does one destroy a parallel timeline?