"Who are we to decide as to who is right or not???"
Please note that if we follow the Messenger then we should know right from wrong!
Your quote above is a cop out of your responsibility to spread truth and justice to everyone as this is a core principle of the Quran. By following the Sunnah of the Messenger, the Sunnah of Allah as revealed in the Quran, you are then able to discern the truth from the falsehood and advise those who do wrong to cease. If they do not listen then that is their choice but you have done your job.
Muta is haram, as is hallalah in sunnism, but both sides cannot see the wrongs they do precisely because they do not judge from the Quran, and are all not submitting to Allah which makes every sect and those who cannot decide right from wrong what?