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Sexton, 30, has suffered several concussions and was forced off in the 69th minute of Ireland's defeat by France on 13 February.
Jones said: "We target players all the time. That's part of rugby isn't it?
"I'm not saying Sexton is a weak defender, but we're going to target players because we want to win."
Jones added that coaches have picked out particular opposition players in their tactical plans "since Adam was a boy", revealing that he had told his players to run at England fly-half Jonny Wilkinson's injured right shoulder when coaching Australia in the 2003 World Cup final.
The treatment meted out to fly-half Sexton in Paris - including an off-the-ball shoulder charge by second row Yoann Maestri early in the first half - was criticised by Ireland coach Joe Schmidt.
Maestri escaped a ban after the incident was reviewed by the citing commissioner. Sexton was diagnosed with whiplash injuries to his neck and shoulder after the match.
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Jones said that he wanted England to be "brutal" but legal in his first match at Twickenham since taking charge of England in November.
He said: "It's not illegal to target someone. I don't want our players to do anything illegal in terms of the laws. We want to be physical, fair and brutal.
"They've talked about him having whiplash injuries, which isn't a great thing to talk about. I'm sure his mother and father would be worried about that."
Captain Dylan Hartley added: "If there's a weak defender in the team, you put your best ball carrier at that weak defender. But a weak defender could be a lazy tight-head whose legs have gone. It's not because they're physically weak, it can be for other reasons."
Sexton spent 12 weeks on the sidelines between November 2014 and February 2015 as part of a enforced lay-off following a four concussions in a year while playing his club rugby for Racing Metro in France.
Some media commentators have called for Sexton to consider retiring to protect his long-term health with 69% of readers responding to an online poll by the Irish Independent newspaper suggesting he should stop playing.
Former England scrum-half Matt Dawson told BBC Radio 5 live that Jones' comments were "refreshing".
Dawson said: "Of course he has not overstepped the mark. That is the way that it is. Every single meeting between England and Ireland, they will have been targeting players they think are weak."
Ireland fly-half Johnny Sexton will be a legitimate target during Saturday's Six Nations match at Twickenham, says England head coach Eddie Jones.