Modern-day terrorism is a recruitment scheme. Any attack has the effect of increasing hostilities between groups. Imagine being a teenager with an identity crisis who happens to be part of a minority that the less intelligent half of your home country hates and despises. What group are you most likely to join? And what caused said hate and despise to grow? Right, terrorism.
More generally put: Virtually any organization has as its own survival as a high priority goal. Organizations on the extreme ends of ideology, any ideology anywhere, will benefit from increased hostilities in a population. It pushes more people to the fringes.
Terrorism is a time-honoured way to increase hostilities. The moderates lose, the the extreme ends on all sides win (whether you're Trump or ISIS).
Look at recent history and see how well it worked. American bombs on funerals, ISIS bombs on French crowds, it's all terrorism and it works wonders to keep the perpetrators powerful.
When Anders Breivik killed an island full of people, then-prime minister of Norway responded to like this:
"The Norwegian response to violence is more democracy, more openness and greater political participation"
This is the correct response to terrorism and we need a lot more of it. Once you see terrorism for what it is, a recruiting scheme, then it is obvious that "powerful language", "bias to action" and all that shit that politicians usually do, is very counter-effective.