For some additional perspective, the Obama family detention initiative —which, note, did not include systematic family separations — was launched on June 20, 2014. Over the ensuing months, the left rose up against it and lawsuits were filed. By May 2015, most Dems in Congress, plus candidate Hillary Clinton, were publicly calling on Obama to halt the program. A federal judge ordered it to be halted on July 24, 2015, which was the beginning of the end. So, 13 months for opponents of the policy to achieve success.
In comparison, Jeff Sessions announced the administration's "zero tolerance" policy on April 6, 2018, although the family separation policy actually started on a smaller scale in July 2017. Even using April 2018 as the start, we are 15 months in and it is getting worse and worse. 15 months until they started getting called concentration camps. With no members of the president's party calling for the end.
So, even aside from the fact that Trump's policies are significantly worse than Obama's, and even aside from the fact that the left did vocally oppose Obama on the issue at the time, the timeline is an additional reason why the rhetoric is getting more heated right now. And rightfully so.