Doesn't the lasso kind of go against everything Diana stands for?

[DochaDocha]

The lasso is just a tool. It's not inherently good or bad, but it can be used for either depending on its user. There've been a handful of stories in which she used the lasso to bring someone to his/her senses or bring the truth forward in a constructive way other than just ensnaring a bad guy and getting him to fess up.

[Silvanus]

I see the OP's point: one of the ideas the character has always stood for is freedom, and an instrument of coercion does seem to symbolically go against freedom.

But her creator's ideas about freedom were..different. William Marston thought that what men really wanted--deep, deep down--was to be ruled by loving, beautiful, strong women. For him, being bound by the lasso probably represented freedom from will and from superficial desires, and freedom to be bound by women. He really thought that freely giving up free will (paradoxical as that may be) was the one way the human race could move towards peace, as long as the people we'd submit to would be truly loving women. So you can see why the lasso made sense to him.

For those of us who don't fully buy into Marston's philosophy, the lasso can still represent relative non-violence. In an imperfect world, relative non-violence--such as a weapon designed to hold without hurting or harming--may sometimes be the best we can get, realistically. When Marston was creating Wonder Woman, even Superman (not to mention Batman) was pretty brutal in using the threat of force to coerce people to confess or surrender, so I get how the lasso looked (and can still looks) like a relatively non-violent alternative to swords, guns and fists.

And I suppose Wonder Woman's philosophy could be that "the truth shall set you free"--once villains have been made to confess, they can start to reform, and reform is their chance at true freedom, which would include freedom from all the baggage that made them villains in the first place.

[Vanguard-01]

Messner-Loebs showed Diana trying to talk criminals down quite often early in his run (pre-Deodato), showing that Diana was willing to put herself at risk to end hostile situations peaceably. He really got this aspect of Diana.

Wasn't his run also the run where Diana stood still and pretty much let Cheetah slice her to ribbons while trying to talk her down? Another good example of Diana's peaceful, compassionate side.