This mode of protest does not make sense.
First: Once a book is brought ,author get his royalty. Subsequent sale and purchase doe not lead to any gain for publisher and author. This is the reason why publishers and authors hate ,and try their best to limit, second hand book market.
Second: If someone is thinking of returning books to publisher, he would find that either he could not do so, or there is a time limit for returning a book.
Third: These authors may have won an award ,but most of them are rank mediocre. I have read their award winning pieces on twitter when it trended. Some were pure pornographic stories, other were class II poems, and the only award for Sanskrit literature ,since independence, has been granted to someone who wrote "Indira charitra". These authors could not recover even price of binding from direct sales. They depend upon their work being prescribed as recommended study in Universities,and bulk purchases by library.
If you want to hurt them than destroy their ecosystem, rather than these juvenile kind of protests. First of these would be to bankrupt small leftist publications who provide leftists a cheap platform to start their career. Most of them are not financially sound ,and in absence of patronage, could be driven into the ground by litigation costs. Thus it would be much better for people to find some offending part in work of the author they want to target and drive that author and his publisher into court. Winning is immaterial. It is fighting that would count. Second: Government should blacklist award returnees and should not show them any hospitality in future (no awards, no official accommodation, no seminars/study tours in taxpayer's dime), and instruct libraries and Universities it control (real control, not JNU type control) to not prescribe or buy works of these authors, though there are enough leftist Uni's ,who would prescribe their book as course material, and Congress ruled states ,who would buy their work in bulk, that they could survive a mildly hostile BJP.