Even if Michael is bi I doubt he's Christian's type or that Christian is his type. He could try it on with Jack and get rejected of course but that's abiout it. Besides I hhave always thought of Syed/Christian as being on a par with Sharon/Dennis. And, Christian is exagerating the kiss with the piper. The kiss came from the piper's side not his. The piper brushed his lips against Christian and Christian backed off.