People who work without pay are either volunteers or slaves. I doubt that many government employees working without being paid during the shutdown consider themselves volunteers. United States citizens should not be enslaved by their government for any reason. Government employees not being paid should walk off the job en masse (usually called a strike).
The real national emergency is not the wall. The real emergency is government workers being furloughed or working without pay. Establish an emergency fund to pay workers during the shutdown, if necessary. Give them the means to support their families while doing the jobs they’ve been hired to do to serve us all.
Congress should not allow itself to be blackmailed by President Trump. Congress (both Democrats and Republicans) should vote to open the government. All functions should be fully funded except border security. Then, funding border security can be discussed in a reasonable atmosphere for negotiation.