Its not so much that they enjoy killing the unborn, its the vast amounts of money the abortion industry provides to their cause.
I think their motive is more nuanced than either of those.
In order to advance its Marxist agenda, and rob us of our Liberties, the Progressive Left needs to get past the ultimate firewall - known as the US Constitution - the Bill of Rights. The Constitution is what makes the USA a self-governing Republic.
They need to discredit it, defang it. To do so, they need to find wedge issues by which they can argue (falsely) that the Constitution, as it stands, is corrupt from its founding, and actually infringes upon our freedoms rather than protecting them.
One such issue, their flagship issue, is abortion (or choice, as they call it).
According to their perverse argument, the Religious Right has weaponized the Bill of Rights - Religious Freedom infringes upon a womans reproductive rights. So-called Religious Freedom is not freedom - it is Tyranny according to the alert.
This is what the Left does with issue after issue: poverty, racism, equality, choice, gun proliferation, you name it.
They dont care about the issue or the people supposedly affected - they care about their political agenda - which is the discrediting, debunking, defanging of the Constitution, which is an obstacle in their path toward total State control.
I think their motive is more nuanced than either of those.