It's a complete non-argument because
a) It can be used to counter anything. Why do you do X instead of feeding the hungry, educating the poor and healing the sick? And when you in fact do feed the hungry, someone says "gosh, why don't you educate the poor instead?" It is just a lazy refutation stemming from personal objections that can never bear the brunt any argument. To even give such call to arms some substance, you have to prove a causal link where X siphons money from Y or how the money from X could actually find a way to Y.
b) LHC is a united effort. Even the single biggest contributor, CERN, doesn't add more than 20% of the funding. Then you may add individual country donations, worldwide university donations, private donations... good luck coordinating that money to any other project, nevermind the fact that most of those contributions would never go to anything else. CERN is all about particle physics. Companies like Alstom are into physics. Physics departments on universities as well. A significant part of the budget is not redirected from other branches of science, it is available precisely because it is LHC. The money snowballs since it's a trendy project and attracts money that wouldn't have to land in science anyway.
c) The law of diminishing marginal utility. Some people think that if we threw billions into the research of AIDS, we would find a cure in no time. Wrong. There is already a substantial amount of money in that research. What would increased funding accomplish? It would attract more scientists. The bad ones. The passionate and those with expertise are already doing research in that field. Attracting those with passing interest and borderline insufficient expertise only leads to duplicity of research and plumetting marginal utility of research, i.e. inefficient use of public money. On the other hand, Tevatron clearly reached its boundaries and could not serve further in the research at cost-effective pace. If you have a discipline where you need only 1 main project to do the heavy work, it's damn clear that if you have 0, you are in fact underfunded. That doesn't mean the project is perfect - I would eliminate the Chinese wall between CMS and ATLAS teams since they are pretty much separately duplicating research while the accuracy boost in their findings is marginal and the cross-checking doesn't need two separate teams - but it's necessary for particle physics. It is also well-designed, with clear goals, strategy and long-term planning including future upgrades. Can't say that about "shovel-ready" project the money could potentially flow into should LHC be shut down tomorrow.