There are very few charges that can’t produce countercharges. Every campaign has a narrative for itself and a counternarrative for its opponents (watch what the Democrats will try to do with Giuliani’s crime record in New York City). Fred Thompson is running not just as conservative comfort food, though that is certainly part of his appeal — he is taking advantage of conservative nostalgia for times, real and imagined, when Republicans were seen as more principled. He subtly exploits Reagan nostalgia; he much less subtly exploits 1994 nostalgia (the latter a huge driver of fantasies on the right that a figure as unpopular as Newt Gingrich would make a viable presidential candidate). The other years you mention just don’t have the same place in the conservative imagination as 1994. He didn’t pick that year arbitrarily — picking a year when he backed the same campaign finance reform law that all his top-tier opponents also supported would be arbitrary.
The other candidates’ resumes may trump that nostalgia — judging from the statements you quote, they certainly hope so. But it will still be true that Thompson was part of the Republican congressional takeover the same year that Rudy Giuliani endorsed Mario Cuomo and Mitt Romney was running away Ronald Reagan. (John McCain hadn’t done much wrong from a conservative perspective by that point.) The other candidates just have to argue that there are more important things for the voters to care about, and perhaps they will succeed.