Other brands that have aroused howls on social media include athletic clothing and equipment brand Under Armour after its chief executive praised Trump, and sporting goods chain Dick's Sporting Goods that restricted some gun sales. Third-party sellers can sign up to advertise products on Walmart's website, and the retail giant gets a commission on each sale.
However, MAGA merchandise is still available.
The hashtag #BoycottWalmart became a trend on Twitter as users railed against the company.More news: Suarez to Griezmann: Stop pretending to be Uruguayan
Furious Trump supporters see the clothes as evidence that Walmart has aligned itself with America's political left, or that it is trying to send a partisan message.
And he said the idea of impeaching the 45th USA president went a step further than the MAGA gear, which expressed support for Trump and could be offset by equivalent products on behalf of Democrats.
The members of the Walton family - most prominently Jim, Rob, and Alice - generally hold conservative political views that align with President Trump's policies. Amidst the many "Make America Great Again" tees, the company also sells shirts that are critical of the president.
It's unclear whether these are one-off incidents, or whether Walmart is systematically removing anti-Trump paraphernalia from the site. Walmart hasn't responded to media inquiries seeking a response to the boycott threats. "Tree. Journalist. Some assembly required", after facing massive backlash.
Walmart came under fire for another incident last November when customers noticed a shirts that read, "Rope".