I've done a bit more research into the legality of "lolicon" content in the US (where SDF is hosted). IANAL, however, Federal law 18 U.S. Code § 1466A states:
Obscene visual representations of the sexual abuse of children
(a) In General.—Any person who, in a circumstance described in subsection (d), knowingly produces, distributes, receives, or possesses with intent to distribute, a visual depiction of any kind, including a drawing, cartoon, sculpture, or painting, that—
(1)
(A) depicts a minor engaging in sexually explicit conduct; and
(B) is obscene; or
(2)
(A) depicts an image that is, or appears to be, of a minor engaging in graphic bestiality, sadistic or masochistic abuse, or sexual intercourse, including genital-genital, oral-genital, anal-genital, or oral-anal, whether between persons of the same or opposite sex; and
(B) lacks serious literary, artistic, political, or scientific value;
or attempts or conspires to do so, shall be subject to the penalties provided in section 2252A(b)(1), including the penalties provided for cases involving a prior conviction.
The Department of Justice's Citizen's Guide To U.S. Federal Child Exploitation And Obscenity Laws states that "lolicon" is illegal and has a lower standard than obscenity in adult pornography.
In addition, Section 1466A of Title 18, United State Code, makes it illegal for any person to knowingly produce, distribute, receive, or possess with intent to transfer or distribute visual representations, such as drawings, cartoons, or paintings that appear to depict minors engaged in sexually explicit conduct and are deemed obscene. This statute offers an alternative 2-pronged test for obscenity with a lower threshold than the Miller test. The matter involving minors can be deemed obscene if it (i) depicts an image that is, or appears to be a minor engaged in graphic bestiality, sadistic or masochistic abuse, or sexual intercourse and (ii) if the image lacks serious literary, artistic, political, or scientific value. A first time offender convicted under this statute faces fines and at least 5 years to a maximum of 20 years in prison.
The Fourth Circuit Court of Appeals has upheld a conviction under 1466A in UNITED STATES v. WHORLEY (2008).
The Lemmy instance Burggit explicitly allows "lolicon" content:
Cooking up a platform for Free Thought And Expression! (NSFW & Loli/Shota/Cub friendly!) Minimal Restrictions on Content/Speech.
Since Burggit hosts content that is illegal in SDF's jurisdiction, I would support SDF defederating from Burggit.