Yes, this is the exact problem. When the Democrats cave to the Republicans on this issue, the Republicans just find room further to the right and keep dragging the Democrats with them in that direction.

For the far right, the border will never be secure enough. If the border is not now secure, it is most assuredly the Republicans' fault. What in the hell were they doing for nine years? And how come nobody will ask that question of them? Instead the left makes concessions, saying "Yes, we agree about border security. Let's put into place really fascist deportation policies and just hope that at some point the Republicans finally agree to talk about legalizing the handful of lucky people who are still in the country after the dust settles."