The short answer is: Yes, it's bad.
The long answer is, logically, a bit longer :P
As the most used search engine is Google, we should take a look about what Google does and doesn't like: check Google Information for Webmasters
I've quoted a point that answers your question:
Offer a site map to your users with links that point to the important parts of your site. If the site map is larger than 100 or so links, you may want to break the site map into separate pages.
Note that they suggest you to break the sitemap when it reaches 100 or so
links. You have to care that this 100 is an orientative value, and the or so
is an indication that you shouldn't worry too much about the difference among 100 or 101 links. So, if your sitemap is close to the 100 links (even if it is a bit larger), you only have to worry about splicing it if it is expected to grow larger. Otherwise, if your sitemap has 200 links or so, you should try to split it to some pages to keep them smaller.
Another point to care is that a sitemap is not needed to link each and every page on the site, but only the important parts of your site
Also, a user will navigate easierly if there are 80 links, for example, that if there are 240. Quoting again the Guidelines:
Webmasters who spend their energies upholding the spirit of the basic principles listed above will provide a much better user experience and subsequently enjoy better ranking than those who spend their time looking for loopholes they can exploit.
So, in the case that the sitemap is 100 - 150 links or so (the intermediate point that could raise doubts), the ones who could really tell you if it should be split are your users.
To finish, I want to comment the most extreme case. If the sitemap is VERY large, then when spliting it to files with less that 100 links could even produce more than 100 files, and then the page that links to these parts would have more than 100 links, and it would need a new splitting. But you only have to care that if your site is bigger than 10.000 uri's, and this only happens in very large sites like G, MS and so.
Hoping be useful
Webmaster & Programmer
PS: Welcome to WebmasterWorld! ;)
PPS: I try to write the best I can, but it migth be not enough. If you find errors (either syntax/spelling or content), please let me know to fix them.