Spice Jet Airlines — Refused travel on invalid reasons

Address:

Jaipur, Rajasthan

I am a doctor working in Dubai, UAE with NRI status and my family is in Jaipur, India. I or my family keep on travelling regularly between Jaipur and Dubai. Since I have only foreign credit card, hence I book my airline tickets for me and my family through this foreign credit card.
Recently, I faced lot of harassment by the Spicejet airlines staff on which I had booked my ticket for travel from Jaipur to Dubai on 30 May 2017. At the Jaipur boarding counter I was asked to show the credit card through which the ticket was booked. Since I have numerous foreign credit cards and I cannot carry all of them during my travel, and I was unaware of this rule or requirement; hence I did not have the credit card and I was refused for travel, and had to book a new flight ticket again. Earlier, I or my family has been travelling repeatedly on Spicejet through my foreign credit card booked tickets, but was never asked to show the credit card.
The Spicejet airlines showed me the terms and conditions of their airline which states that 'For all foreign (Non Indian) credit/debit card payments, the card must be produced for physical verification at the airport check-in counter if the passenger is the cardholder. In case the card holder is not travelling, it is mandatory for the passenger to furnish to the airport check-in staff a physical copy of the front side of credit/debit card duly authorized by the card holder, along with cardholder's valid proof of identification and passenger's valid photo ID proof'. The airlines have refused to address my concerns beyond this rule.
I have been using these foreign credit cards for numerous transactions and travels worldwide, but so far have never been asked to show the credit card by the mercantile.
1) Is this rule by private airline carrier legally valid to refuse me travel?
2) Can such discriminatory rule for only foreign credit cards be made by such private agencies?

I am writing to you after lot of desperation and with full hope that you will address this discriminatory, illogical, illegal and user unfriendly rule, so as to avoid harassment to the public affected largely by this ruling