The passage can be found in Chapter One, Calculations with the Chinese text 利而誘之，亂而取之. I translated it as, "If they seek advantage, bait them; if they are in chaos, capture them."
I have bolded the specific sentence in question above. One can also translate it as "take" them or even "invade" them, but "crush" them is careless and misleading. It seems like a small difference but it is not. It is a chasm. It is like hearing the commander say, "Seize this city" and interpreting it as "Destroy this city."
The accuracy of a sentence's translation is one important consideration, but let's also look at that sentence's alignment with Sun Tzu's key principles. If you consider the overall context of The Art of War, the book's advice is clear. Below are five examples of passages that run counter to "crush him":
(1) "Generally in warfare, keeping a nation intact is best, destroying a nation second best; keeping an army intact is best, destroying an army second best; keeping a battalion intact is best, destroying a battalion second best; keeping a company intact is best, destroying a company second best; keeping a squad intact is best, destroying a squad second best." Sun Tzu
(2) "If ten times the enemy's strength, surround them ... Do not thwart an enemy retreating home. If you surround the enemy, leave an outlet; do not press an enemy that is cornered. These are the principles of warfare." Sun Tzu
(3) "One who is skilled in warfare principles subdues the enemy without doing battle, takes the enemy's walled city without attacking, and overthrows the enemy quickly, without protracted warfare. His aim must be to take All-Under-Heaven intact. Therefore, weapons will not be blunted, and gains will be intact. These are the principles of planning attacks." Sun Tzu
(4) "Replace the enemy's flags and standards with our own. Mix the captured chariots with our own and treat the captured soldiers well. This is called defeating the enemy and increasing our strength." Sun Tzu
And last, this is one of my most favorite quotes in The Art of War:
(5) "Those angry will be happy again, and those wrathful will be cheerful again, but a destroyed nation cannot exist again, the dead cannot be brought back to life. Therefore, the enlightened ruler is prudent, the good general is cautious. This is the Way of securing the nation, and preserving the army." Sun Tzu
Critics will say this sort of peace is only temporary. But everything is temporary. In a changing world, nothing is ever permanent. Sun Tzu had the ability to handle war and conflict with aplomb. Therefore, it is better for him to establish peace right now when violence has broken out than to achieve an idealized permanent peace later on. Along those same lines, it is better to start building bridges and wait to be able to complete it in the future -- Sun Tzu's concept of timing -- than to induce, continue, or exacerbate hatred now and crush any hope of success in the future.