When people say that, they do not mean that they are in fact the same person or that they would have taken actions that are literally identical.
What they mean is that either Hillary Clinton would have done the same amount of damage in her own unique way, or that Hillary Clinton would have had the same level of negative impact on those who did not align with her. Sometimes, they mean that both sides have the same level of vapid tribalistic hate, and care for the morals/causes/people that they tout about on the internet only insofar as they can use them as a bludgeon to hurt the other team as it's own end.
I am glad I am here to help with these things.
That's sometimes the case, but there were a lot of Democrats (or former Democrats) claiming that she was as anti-environment, anti-gay, and pro-corporation as any Republican.
Because the environment got ignored during the primary, she didn't stand up for gay rights at the very beginning of her long career, and corporations donated to her (just like every candidate who stood a chance, with one exception).
Oh yeah, and wanting to keep and expand Obamacare also made her a corporatist shill (ironic considering that yes, Republicans had originally floated the same health plan, but de-facto crazy because Republicans were now explicitly promising to destroy that basic level of public health care we'd finally achieved).
We (the left) hit some disastrous combination of over-optimistic, impatient, and jaded. Another 4 years like Obama weren't enough (Congress? That's complicated, blame Obama). We needed true progressive change *now*, from the executive office somehow, and when that fell through we largely didn't bother voting for "good enough". Enough for an upset.