Regarding one or more persons inserting into another's anorectum, rapid thrusting with considerable girth especially for a prolonged duration must constitute criminal negligence at the least, worldwide without limitation.
"Perirectal sepsis is a potentially severe complication which may follow minor anorectal intervention and be slow to be diagnosed and treated. We report the presentation and outcome of three patients with perirectal sepsis of differing aetiologies. Awareness of the possible diagnosis, urgent investigation with cross-sectional imaging and immediate treatment with broad-spectrum antibiotics is vital. However, radical surgical intervention may be necessary. This report highlights the importance of investigating patients with persistent pelvic pain after minor anorectal procedures or trauma and maintaining a high index of suspicion for this important complication."
... "Relatively innocuous surgical intervention, such as open haemorrhoidectomy or lateral anal sphincterotomy, may provide a portal of entry for bacteria that could explain local or indeed distant sepsis (e.g. infective endocarditis following rubber band ligation)."
Annals of The Royal College of Surgeons of England. Jul 2008; 90(5): W4-W7. PMC2645747.
"The human intestine provides a habitat that is rich in nutrients, permitting for the growth of over 500 different species of bacteria, with the highest concentration of bacteria found in the colon. In addition to bacteria, the human colon is frequently exposed to both pathogenic and nonpathogenic viruses. Normally, the bacteria found in the colon have a symbiotic relationship with their host and can even provide some protection against pathogens. However, some microbes that are normally or incidentally found in the colon are pathogenic or potentially pathogenic if they breech the host mucosal barrier."
Cancer Epidemiology, Biomarkers & Prevention. 2008 Nov; 17(11): 2970-2979. doi:10.1158/1055-9965.EPI-08-0571. (PMID 18990738)