Artificial intelligence is never a threat of itself - only when it is deliberately used and directed by one human against another, e.g. CPU controlled "intelligent" bombs, missiles, guns etc.
The only thing that might be of concern would be if a machine were developed that was self-aware. It is however very possible that sentience can only be a part of living organisms, and we have absolutely no idea what "life" is, but it is very unlikely that it would occur spontaneously in a silicon chip.
