Dear Tejwant Singh ji that is not a good approach. Believing in Guru Granth Sahib is a spiritual and personal subject for a devout Sikh if Waheguru so desires depending upon ones Karma.
Serving in the armed forces or any government or other jobs out side India is a matter of livelihood. If we go by your logic then no Sikh should be doing any job even with the Indian Government or any Indian company or organization after the way we have been treated in the past.
Going a step further, no Sikh belonging to the Malwa region of Punjab, where the Phulkian Dynasty ruled during the time of Maharaja Ranjit Singh, deserves to be called a true Sikh. Why? Sikhs and their rulers from that part of Punjab not only remained neutral during the Anglo-Sikh wars but allowed the English to use their territory for war against that part of Punjab where Shri Harmandir Sahib rests. Perhaps a read of ‘The Last Sunset –The rise and fall of the Lahore Durbar’ by Captain Amarinder Singh would put the subject in the right perspective.
For that matter no one’s hands in India are clean. Every community and region has the blood of the others upon their hands. How did the English start from a small trading post of Calcutta and reach Delhi and the borders of Punjab? The Purbia soldiers –Rajputs, Brahmins and Muslims- from Bengal, Bihar, UP and other parts of India fought for the English against their own religious brethren.
If we go by your logic, then one can point a finger even at Guru Gobind Singh ji for helping Muazam, the son of Aurangzeb, to become the next Mughal emperor Bahadur Shah. Guru Maharaj had stipulated two conditions for the support. Unfortunately, Bahadur Shah did not fulfill them after he sat on the throne. When they parted company at Nanded (Hazoor Sahib), Guru Gobind Singh ji told him that he would not rule for very long. The Mughal emperor was killed treacherously in a merciless manner by his own sons in Lahore eight years later. And what all happened to members of the Mughal Dynasty after that is something which had never happened before when people like Akbar the Great were favorably inclined towards the House of Guru Nanak.
If we go by your logic, then no true Sikh should step out of his home.
