The phrase "agreed with the principle" is correct and usable in written English.
You can use it when expressing your concurrence or alignment with a specific principle or idea.
Example: "After much discussion, I found that I agreed with the principle of sustainability in our project."
Alternatives: "concurred with the principle" or "aligned with the principle".
Most critics agreed with the principle of climate change mitigation.
River Island said it agreed with the "principle and intent" of the accord but still had queries to clear up.
He said he agreed with the principle of "targeting all members of Daesh … [but] of course we will need to see how the law and the drafting works".
A government spokesman agreed with the principle of on-site support in schools and said it was already the case in some places.
At the Next shareholder meeting, the retailer's chairman John Barton said he "agreed with the principle" of a living wage but it was "not for us to endorse".
Strictly speaking, it wasn't exactly true — Clinton is leading in the polls with forty-nine percent of the vote — but everyone agreed with the principle.
Each step of the way, the board agreed with the principles that he established and the actions he took.
This randomised, blinded laboratory study was approved by the National Committee on Animal Research Ethics (2014 15 0201-00421; Glostrup, Denmark) and agreed with the principles of Laboratory Animal Care [32].
Delegates were only eligible to attend if they certified they had read and agreed with the principles of Harvey's newest book The Book, which dealt with the harmful effects of usury by the government.
For example, within our own published studies of gender-transformative health programming, men reported that while they agreed with the principles of women's rights in abstract terms, they also felt that in practical terms, rights were 'an affront to manhood' that made women 'too demanding' or that they were being 'controlled' in their relationships with women more generally.
Lumley says she agrees with the principle.
