I think it's in bad taste. It's the Democratic National Convention; not the Barack Obama National Convention. If you can't bring yourself to attend your own party's quadrennial coming-together, maybe you need to find another party.
It is basically the Obama national Convention. Obama took the party and turned it into his own reelection campaign. He tore down the 50 state strategy and completely destroyed the party. If I was a Democratic Congressman from a conservative area, I would proudly endorse Mitt Romney and even campaign with him. I recall some Democrats in the south endorsing Bush in 1988 and Reagan in 1984.