what if they take the bishop
Dutch Trap

6 Bd3 is inaccurate even though White is still clearly better. 6 Be2 is much stronger.
After 6 Bd3, Black can just play ...d5 and suffer from a worse position than an almost positionally busted one he would get after 6 Be2!. Usually Black plays 4...Bg7 or 4...c5 in this system.
These are nice traps, but I think if you guys want to improve at chess, you need to know the point of the move 2 Bg5 against the dutch.
The entire idea of 2 Bg5 is to lure Black into a non-ideal line of the Tromposky or the Verasov, where Black has played the very undesirable ....f5 when this pawn should be on f7. In the Tromposky, 1 d4 Nf6 2 Bg5, white really gets nothing out of the position after 2...d5 3 Bxf6 (3 e3 c5!, 3 c4? Ne4 followed by ...Nxg5 and ...dxc4) exf6.
If Black avoids this by playing (1 d4 f5 2 Bg5) 2...g6 or 2...d6 after 2 Bg5, White gets a version of the Verasov with e3 followed by Nc3, with realistic chances of an advantage, which he doesn't get in the "main" Verasov at all. White can then prepare e4, even though he has lost a tempo with e3. Most people who play the Verasov (1 d4 d5 2 Nc3 Nf6 3 Bg5 Nbd7) would jump at the chance to play White in these positions with ...f5 being played.
One of my favorites, although i’ve never used it in a game.