This should be a Liberal no-brainer. Walls don't work, right? Walls are immoral, right? Walls are Racist, right? Walls cause death, right? Ok then but ask a Liberal "So you want the existing barriers torn down then, right?" Here are the responses you get:
1. Crickets.
2. "Orange man bad".
3. "I like turtles".
Walls more or less work.
Small walls are easy to man and defend.
Large unmanned walls are vandalism targets. But hey, our deficit spender in chief doesn't mind corporate welfare.
Its more a symbolism thing though. Berlin wall / Trump wall. Conservative / Liberal powers of emergency. End of the Republic / beginning of the Empire (Star Wars expansion of presidential powers).
Personally I would have traded for a wall in exchange for a tripling of legal immigration or something. But man, signing a bill to wall out them in this cracker racist country would have hurt.