This won't end well, but it was difficult to find a good remedy to the f4-f5 threat.
With moves like Re3-g3 and Bb3+ coming up, White has an overwhelming advantage.
1...Bxd4 2.exd4 Nf6 3.g4! fxg4 4.Rbe1 gxh3 5.Qxh3 Black is also under pressure.