It's a rather long stretch to say that Henry "stole" the King of France's wife, either more or less. Eleanor and Louis' marriage had been annuled by Pope Eugene III on the basis of consanguinity, as they were related within the 4th degree and hadn't bothered to obtain a dispensation for marriage. Though Eleanor certainly favored this result, the decision to pursue it was entirely Louis'. Had the marriage produced a male heir Louis would have been far less willing to part with Aquitaine (and the Pope less willing to annul the marriage), but after two daughters with Eleanor, Louis and his advisers began to believe that a new marriage would best solve the problem of succession.

What Henry and Eleanor stole was the French King's right to have a say in the marriage of his vassals. This was particularly true in the case of Eleanor. As overlord to an unmarried female vassal, it was by tradition the King's prerogative to choose, or at the very least approve, her future husband. Louis had, perhaps naievly, relied on this traditional 'feudal' assumption to keep Aquitaine within his patronage, but this is one of those places where reality slaps the feudal ideal upside the head. Henry and Eleanor married without the King's approval, without Papal dispensation (they were also related within the prohibited degree) and Louis was faced with a vassal who controlled vastly more of France than the King himself and who, after becoming King of England in 1154, would be in control of more European territory than anyone since Charlemagne.

I can't say what Henry expected from Louis, but warfare did result and Henry, as was the case through most of his life, seems to have been quite prepared for it. First, Louis demanded that Henry come to Paris and answer for his behavior, an order Henry had no intention of obeying. Next Louis entered a coalition with Theobald of Blois and Geoffrey Plantagenet, Henry's brother. Both men had sought to marry Eleanor (tried to kidnap her actually), and now they, the King, and some rebellious Angevin vassals began to move against Henry's fortresses. You could say Henry was taken by surprise, as he was about to embark for England when news of all this reached him, but he moved very swiftly to drive Louis' forces back into the King's domain, suppress his brother's rebellion in Anjou, ravage the Vexin, and basically muscle Louis into a truce within two months.

This was hardly the end of conflict between the Angevins and Capetians over French territory and the extent of French Royal power. Louis' son Philip II would drive Henry's son John out of Normandy and the Angevin territories in 1204, but in 1152 Louis VII was not in a strong enough position to overcome Henry II.

Sources:

Richard Barber - Henry Plantagenet

Alison Weir - Eleanor of Aquitaine: By the Wrath of God, Queen of England