"I truly believe we are on the slippery slope of a mask mandate evolving into a vaccine mandate," the 3-time Olympic gold medalist volleyball player said. "That scares the [fire emoji] out of me."

The 42-year-old posted a lengthy statement on social media Sunday railing against COVID restrictions ... even saying she recently went out shopping without a mask on to prove a point.

"Things won't open up and freedoms won't come back unless we are willing to push back and stand up for them," Walsh Jennings said. "I am willing to fight for the freedoms I have been guaranteed by my constitution."

While Walsh Jennings insisted she understood the severity of the coronavirus pandemic and wanted to find ways to open up while protecting the "vulnerable" ... she was still blasted for her opinion.

Fellow Olympic volleyball Jennifer Kessy called the entire post "selfish." Others said far worse in the comment section.

But, Walsh Jennings didn't exactly back down in a follow-up post Monday ... she apologized if she offended anybody, but added, "I was not looking to do anything but express my belief that FREEDOM IS RIGHT WORTH FIGHTING FOR."

She continued, "I believe we have to stay mindful of the FACT that our freedoms have slowly been taken from us with our consent."

"Using a mask to express my love of freedom perhaps seems a bit shallow and selfish (peoples health are at play, after all), but it is a real thing to point to and it is the potential starting point for so much more."