For me it's a must-win because I'm thinking big picture. Look at Denver and some of the champions in recent years. They kept their foot on the gas pedal and just dominated, even on the road. If the C's are that team, they need to bounceback tonight and assert their dominance.
A loss tonight wouldn't doom them for this particular series because they could tie it 2-2 and still win in 6 or 7, but it'd be a bad look if they had to go 6+ with this Miami team in the first round, and I think it'd be a sign this team probably isn't even reaching the Finals.
Denver, Minnesota are probably on their ways to sweeps or easy 5-game wins. They are two of the Top-3 favorites to win it all including Boston, and also were in that "40/20 club" which includes OKC. OKC is up 2-0 in their series, they took care of business at home to begin the series.
You're just making the path much harder and risking injury by playing with your food and prolonging series. Do you think Minnesota and Denver went on the road up 2-0 and thought, "eh we can afford to drop this, no need to go all out"? Nah they had convincing Game 3 wins too.